Fundraisers may also post Twitter and Facebook optimized campaigns.

It works in the following way. With Facebook for example, you do not need to create Facebook proprietary Fundraisers. It functions more like GoFundme, where all nonprofit campaigns are Facebook optimized for sharing. 

So, Fundraisers create their campaigns on your branded platform first, and next post their fundraisers to Facebook/Twitter. Donors will then click the post linking to your branded fundraiser. They do not click a Donate button in Facebook’s native fundraising tool.