Are you requesting to apply a net capital loss from a prior year to your 2008 capital gain?
Or are you requesting to apply a 2008 loss to prior years?
If the former, you use line 253 on your return.
If the latter, you have to request a loss carryback on a T1A Request for Loss Carryback for that particular prior year. Then you do have to wait a few months or more, because they don't necessarily do the adjustments right away.
http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/rtrn/cmpltng/ddctns/lns248-260/253/menu-eng.html
Or are you requesting to apply a 2008 loss to prior years?
If the former, you use line 253 on your return.
If the latter, you have to request a loss carryback on a T1A Request for Loss Carryback for that particular prior year. Then you do have to wait a few months or more, because they don't necessarily do the adjustments right away.
http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/rtrn/cmpltng/ddctns/lns248-260/253/menu-eng.html