You can add any money you raised offline by updating your offline donation amount via your dashboard.
1) Login to your fundraising page and go on your dashboard
2) Click on the fundraising page you want to add an offline donation to
3) Click on 'edit page' (top right-hand corner)
4) Scroll down until you see a turquoise box with "manage offline donations"
5) Click on the box and add the donation information, including name, amount and any messages left.