You can.
Tactics Trainer > Try Vs. Computer
Do the chess mentor than or computer work out is good :3
Also you can just buy or download one of the free versions of rybka or houdini. not as strong as the full price but they work good for practice on arena. It lets you set up any position and play against it and lots of websites that list practice positions.
If you need help, please contact our Help and Support team.
Hello,
it will be nice if I could "switch colours" and "take back" in the Tactics Trainer option "Try Vs. Computer"
Regards