So, you want to enrich uranium, do you?
It's dangerous and difficult work. First you need your uranium, preferably in metallic form. I won't cover uranium mining here. So you take your metallic uranium, remembering that it is radioactive and poisonous (you did know it was dangerous, didn't you?) and you grind it into a fine powder. React that powder with fluorine.
Take your uranium hexafluoride, a greenish toxic radioactive gas that will react violently with water or water vapor, and run it through many miles of pipes occasionally interruped by screens of extraordinarily fine mesh. This mesh will slow the heavier uranium 238 hexaflouride molecules whilst allowing the uranium 235 and 234 hexafluoride molecules to continue unimpeded. At the far end you will have a slighly higher concentration of u-235 in your toxic green gas. Be happy! Do this a few more times so that you have a usably high proportion of u-235 to u-238. Then remove the fluorine, leaving behind mostly uranium 235.
This whole process, used in the K-25 complex at Oak Ridge back in the 40s, probably just took many many megawatt-hours of electricity and 20 years off of your life. Shape your finished enriched uranium into whatever form you desire, and remember to carefully store all the equipment you contaminated with bits of uranium in a safe shielded place for the next hundred thousand years.
If you wanted a more efficient, less absurdly dangerous and slow process, take a look at an isotron. The U.S. military tried calutrons at the Y-12 facility at Oak Ridge, but they didn't work too well. With modern technology, the isotron is the way to go. Share and Enjoy.
And make sure that you never have too much uranium in one place no matter what form it's in. You don't want to die just yet, do you?