With a screwdriver - they're just normal screws which unfortunately screw into cheap plastic mountings - which sometimes rotate and you find yourself screwing for eternity (if only!) and getting nowhere.
If you find that happens, you can get your hand on the mounting from behind to stop it rotating. Worst case, pull it out and the mounting will come out with the screw. You can then unscrew it by hand and insert the mounting back into the dash when re-assembling. You might be able to detect I am not a mechanic!

You don't need to take out the fusebox to access the blower motor housing.
There are 3 screws on the bottom of the blower housing - the motor drops out from below.
Everything you need to know about dis-assembling the fan motor you can find out by reading the earlier posts in this thread.