Composting

We have a bin left from the previous owners. Time to put it to use. I peeked inside and there is a pumpkin and grass clippings from 3 years ago. Looks like I need to get some help...

From the Southern Idaho Solid Waste website:

What Can I Put in My Compost?
Kitchen scraps such as coffee grounds, eggshells and fruit and vegetable scraps; grass clippings; hay or straw; leaves (dry or fresh); manure (NO pet feces!); untreated wood chips or sawdust; shredded paper (newspaper, cardboard, etc.); wood ashes; garden trimmings (NO weeds that have gone to seed)
Where Should My Compost Bin or Pile be Located?
The bin or pile should be located in a convenient place so you don't have to haul materials or compost a long distance. It should not be placed next to the house or garden shed, because moisture from the compost may damage the walls or foundation. It is best to choose a location out of direct sunlight so that the compost stays moist.
My Compost is Attracting Flies/Rodents/Dogs: What Should I Do?
Make sure all food scraps are buried in the center of the pile, and cover the pile with a layer of dry, brown material to mask odors.
What Materials Should Not Be Composted?
Stay away from pet feces (which can carry diseases), fatty foods or products like butter or mayonnaise (which won't decompose easily), and meat scraps (which can attract pests). You should also be careful when composting weeds--any seeds can germinate in the garden when you use the finished compost. In addition, if your lawn has been treated with a long-lasting (one application lasts the whole season) herbicide like clopyralid, you should not compost the grass clippings--the pesticide does not break down and can kill any plants treated with the finished compost.
My Bin Smells Bad: What Should I Do?
This is probably due to too much green material in the pile. Try adding some dry brown material to the pile, mix the pile well to aerate, and cover the pile with a fresh layer of dry brown materials.
Where Can I Get Rid of My Heavier Yard Trimmings (shrub and tree trimmings, etc.)?
Clean branches can be taken to your local SISW transfer station. See the Wood Waste Recycling page for more information.
Is it OK to Put Fresh Grass Clippings in My Compost Pile?
Yes. The large amounts of nitrogen and moisture in grass clippings will help speed up the composting process, but be careful to mix in some brown materials to keep the grass from becoming a smelly, slimy mess.
Can I Add Something to Speed Up the Composting Process?
The best way to speed up the composting process is to make sure you have a good ratio of green and brown materials, to keep the pile adequately moist, and to turn the pile frequently. Commercially available compost additives don't contribute any magic to the process--usually they're just a high-nitrogen organic fertilizer that will help heat up the pile if you don't have enough green material in the mix.
The lawn and kitchen scraps you put in the compost pile generally contain all the microbes you need to get composting started. The best source of composting "bugs" is finished compost or a shovelful of garden soil.
Will Compost From Walnuts "Burn" My Garden?
Ah, the infamous "Walnut Wilt" question. The key here is what type of walnut tree you have. Black walnut trees produce a substance called juglone that is found in the buds, hulls, roots, leaves, bark and stem tissue of the tree. This substance helps make these trees great survivors in nature, but when composted, can stunt the growth of certain other plants to which the finished compost is applied. Other walnut trees do not produce juglone, so you don't have to worry about compost made from them.
As a rule of thumb, black walnut leaves are not a problem if they make up no more than 1/3 of the raw materials in a compost pile. This is because the leaves have a lesser amount of juglone and decompose rapidly. Black walnut hulls, on the other hand, contain a higher concentration of juglone and do not decompose very quickly, so they should only be added to the compost pile sparingly, if at all.
Incidentally, the plants that are most sensitive to juglone include apple, asparagus, azalea, birch, blueberry, cabbage, ornamental cherry, chrysanthemum, crabapple, eggplant, lilac, linden, saucer magnolia, narcissus, pear, peony, pepper, petunia, pine, potentilla, rhododendron, and tomato. Wood and bark chips, shredded leaves or sawdust from black walnut trees should not be used to mulch these plants.