I was arrested in the Central District of California, but my case originates in Ohio (or some other federal district). How will I get to that other district?

If you are in custody, it is the Marshal’s duty to transfer you to the charging jurisdiction. If you are out on bond, you must travel to the originating jurisdiction yourself.  There is a statute — 18 U.S.C. section 4285 — which the magistrate judge can use to order the marshal to pay for your transportation; however, the marshals typically only pay for one-way travel. You should discuss this with your attorney.