Do you have debris in the pump itself? Is it the sort of thing that you can remove the pump/motor assembly and then flush it out with a hose?
If not you have to first remove the strainer. Take the clear top off and take out the strainer basket. There is a C clip inside the strainer housing that holds the strainer body to the pump inlet. Remove this C clip by pulling up. You should then be able to slide the strainer housing off.
If you have one of the newer power flows, there is a button you can press to rotate the discharge from horizontal to vertical. This may help in getting in there to remove whatever is blocking the impeller.
If you still cant get out the blockage, you will see 8 screws that you can take out to remove the pump cover and expose the impeller.
If you do that last step, be careful not to mess with the seal that is on the motor shaft - unless you want to buy a new one that is.
-dave