Log into yourPayPal Website Payments Pro account.
Under the My Account tab, click on Profile, and then on My Selling Tools.
Under "Selling Online", click the Update link for "API Access".
Where it says "NVP/SOAP API Integration", click the link "View API Signature".
Now you can create and/or copy your API Username, API Password, and Signature.
Do not share this information with anyone else and keep it confidential.
Place this information into RaiseDonors at "Account Settings", Merchant Account Tab.