If your campaign has received a large number of donations offline, rather than enter them one by one you can just change the total amount raised and number of donors displayed on your campaign page.
NOTE: You're not actually creating donor records, just changing what's displayed in these boxes:
Sign in to your WeDidIt account and select 'Campaigns' from the menu in the top left.
Click on 'View Campaigns' then 'Edit Displayed Totals'.
Select the campaign you're adding contributions to and enter the total additional funds raised and total additional donors then click 'Update Totals'.
NOTE: This resets every time you re-enter additional funds raised and additional believers. So if today you have one offline donation from one donor for $100 and tomorrow you get another $100 donation, you would need to enter $200 and 2 additional believers (i.e. you'll need to do the math before entering each new update).