If you’re unsure where to find your details you can follow Paypal’s Guide here!
Under NVP/SOAP API integration you’re looking to view your API Signature
Your API signature should have the following format:
API USERNAME:name.company.co.uk
API PASSWORD:WVCK1CTN123U8B
API SIGNATURE:FTN3Gey4Tg7sav5oKlP-ZCBMSF24HKqWr6Yipo9UUeQsjbwRrg-QDxZX