You ask a very large question ...
To develop film you will need, at a minimum:
Developing tank & reels You need to load the film on to the reel and put it in to the tank in total darkness - after that, everything else is done in normal light. If you can not blackout a room, you will also need a large changing bag to load the film on to the reel and tank.
Thermometer made specifically for photography
Measuring graduates (two or three from 10ml to 500ml)
A clock or timer
Developer of your choice
If you want to develop colour film, you will need a large bowl to fill with hot water to put the tank in to keep the chemicals at the required high temperature.
To enlarge, it gets more complicated as the options expand as to which type of enlarger, what formats you will use now and in the future, how much you are willing to spend and what is available in your part of the world etc...
Probably the best thing initially is to visit your local library where you should find a suitable book or two. Then, if you have a specific question feel free to ask any questions about methods, materials or equipment.