If you are trying to assign your Donations form to a Saleforce campaign, by selecting it in the Integrations tab, but you aren't seeing your Campaign in the list to select from:
1) Try clearing your cache. Click the "gear" icon in the upper-right, and click the "Clear Cache" link. This will clear Soapbox's system cache, and force it to queary Salesforce and look for any Campaigns that aren't listed. Try that, and take another look to see if your Campaign is now appearing.
2) If it's not, confirm that your Campaign is set to "Active" by opening it up in Salesforce, finding the "Active" checkbox, and making sure it's checked off. Soapbox will only display Campaigns that are marked as Active.
3) If you've done both of the above, then it's likely there's a deeper issue. Please open a ticket with our support team, and we'll be happy to help you further!