How I got Marksmen to Train at an Archery Target...
Step one. Uniform...
Make a New Uniform in the Military List, Make sure that you have Crossbows selected and that the Squad is Assigned that uniform. Also added a Rudimentary uniform that included all Leather Equipment. Also make sure you have made a few Quivers as they will not train without them. Or go into combat at range as a matter of fact...
Step Two. Ammo.
Press the Ammo Tab (f) and then press c to add ammo, choose bolts then press SHIFT+C, capital C, this will remove a Red (or Green can't remember of top of head) Letter located at the side where there is a TC, the T represents Training while C represent Combat. Clearly you can guess what this means. Ammo with a T only will be used for Training while Ammo with a C next to it will be used for Combat. Its best to rework it so that the Material is ready, also make sure you are pumping out Wood/Bone bolts and metal Bolts in proportion to your Battles, Wood is more surplus then Bones in the early stage due to Critters leaving Partial Skels now instead of plan old bones when killed in combat...
Step Three, Archery Range.
In the old edition you could make a range from One target, now days its better to make the room overlap like you most likely do with Barracks (overlapping rooms made from a Rack and a Stand (or any mixture) Include as many Targets as you want and make sure they all have the room 'T' for training for your Marksmen Squad, double check as it might be that you are selecting your Melee instead as they will appear there too...
Step Four, Waiting...
After a while they should notice that there is an Archery Range there and as long as you are pumping out a large amount of ammo (they are produced in stacks of 5 now from a single lump of wood) you should see action at your range...
This all should work.