After loading the save, you can watch the only marksdwarf squad idling in the meeting area with "Soldier (no activity)" even though they have crossbows, they have metal bolts assigned for combat-only & they have wooden bolts assigned for training-only, there plenty of each stockpiled nearby without bins, *and* the squad is assigned to train at a properly configured archery range.

Next, you can either:

1. Edit the squad's equipment/ammo and toggle metal bolts to be for combat *and* training.... they'll near immediately go start practicing at the archery range with the metal bolts.

OR

2. Create a barracks in the empty space in the room next to the archery range and assign the squad to train there *without* modifying the combat/training ammo designations... they'll probably organize a demonstration first, but after that they'll begin training with the *wooden* bolts at the archery range while *also* carrying the metal bolts reserved for combat.