This is quite a long answer, because your asking how to set up a darkroom.
You've got a good start witha nice enlarger. What kind of lens does it have?
You need some photo trays to put your chemicals in. Then you need basic chemicals like a print deveploper, stop bath(can be water), fixer, and a wash (again, water)
Get yourself a basic B&W photography book. They will go through the how-to of a darkroom.
Exposure depends on the neg. You want to close down your lens to say f8 or f11 and start at a given time. I use 4sec. I hold a piece of cardboard and expose for 4sec moving the cardboard about 2 inches at a time. That way you have a test that has exposures of say 4,8,12,16,20,24 etc. then from there you have some kind of idea of your exposure time.
Again, this is something that would be covered in a basic photo book.
As you set things up, don't hesitate to ask more questions.