[1] Log into your control panel and from the left (off canvas) menu, select 'Settings > Payment / Currency'.
[2] Select 'Test (Sandbox)' or 'Live' mode, depending on your preference.
[3] Click the 'Parameters' tab. Add a single parameter called 'email' and it's value will be your Paypal premier / sandbox / business email address.
[4] The following parameters are optional and can be included if you know what they mean:
'locale' = Valid Paypal locale
'pagestyle' = Valid Paypal page style