When setting up your GoCardless integration, you will be prompted to enter the direct debit mandate URL into GoProposal.
Getting The Mandate Link From GoCardless
Step 1. Login to your GoCardless account and go to Customers > Add Customer
Step 2. You should find a link in the format 'https://pay.gocardless.com/...'
Step 3. Copy this and paste back into GoProposal
GoCardless for Xero Users
Copy the mandate URL from your GoCardless for Xero account by going to Settings > Xero Settings > Xero Automation.