How do I turn basement space into bedroom?

It depends on how big the basement space is. You have to build the walls properly, up to code. You may have to get permits because you will have to put in wiring for outlets, lights, etc. and have it inspected. How finished is the basement? You need to plot out on graph paper what the dimensions of the room are going to be, allowing for the thickness of the walls to be put up, where you want the door, the size of the closet, etc. You need to make sure that it has access to outside in case of an emergency (like getting out a large enough window. If the area has no windows, it isn't considered a livable space. You should perhaps speak with a pro about what needs to be done to see if it can be done DIY by you or not. A lot depends on your city codes and regulations.

25 tips for turning your basement into a bedroom: https://www.familyhandyman.com/basement/25-tips-for-turning-a-basement-into-a-living-space/view-all/

The basement needs an egress window, and a ladder to get up to ground level. I had to install one in house no. 2, it took most of my tax return to do it. It also needs a wall to hold back the earth.

It needs to have large enough windows to escape out of, or a walk out door in room to outside, to be a legal bedroom. Draw out a floor plan to scale (can use 1/4" grid paper. One square is a foot.) Plan your furniture, closet space, etc. You'll have to frame up spaces, do the electrical , insulate and drywall.

You need to frame the walls with two by fours then add plastic for vapor barrier for mold and dampness if you don't care just put paneling

The walls are there , outlets,wiring ECT.just need direction on flooring and celing