If you have 2 cans (4lbs each), you could:
A) Use both cans and no other fermentables (sugar or DME) This will be ok, and if you like hops, it will be great.
B) Get about 6 lbs of DME(3lbs for each batch), and you have 2 seperate 5 gallon batches as the 4lb can was made for use in 5 gallon batches. While your at the store getting the DME, get about 2 oz. of cascade pellets. Boil the hopped kit and the DME together for about 15 minutes(mixed with water) and add 1oz of cascade when you turn the burner off. Cool in your sink and top off to 5+ gallons with cold tap water. This is the way I would go. Then you have two 5 gallon batches out of those 2 cans your sitting on!! Any dry ale yeast(even whats supplied under the lid) will do the job and in about 2-3 weeks, go ahead and bottle. Whatever you do, don't follow the directions on those cans. Come back to homebrewtalk and ask everyone here if you have questions.