In your globals file you have the following setting:
$WAGLOBAL_Shipping_Enabled
You can set this to false to have it not do the shipping while you are working on getting the PayPal going.
When you are ready to use shipping you will set this to true. To setup the shipping you will need to get your accounts setup with the various providers first.
PowerStore is designed to work with a single shipper that you choose between the three. It is possible to customize the store to allow for more than one choice at a time based on a user selection but this is a little more advanced. I would suggest that you get the shipping going for a single provider before trying to do this part.
If you need some more info on these settings in the globals file or setting up the accounts please take a look at the following PDF:
sp_ps_globals_2.pdf
You will want to checkout the section titled 'Shipping Settings'.
