If the offender is being released to bail, the posting of bail must be recorded before the release itself. You record posting of bail on the Bail/Bond screen.
If the offender has multiple orders with set bail, you must post each bail item before the offender can be released. (You can leave this screen without posting bail for all orders, but if you then attempt to release the offender, the Release screen will warn that the offender still has active orders.)