To set up a memorial fundraiser, you must first create a memorial website. You can create one here:
Once you've created your website, make sure you're on 'Edit Mode' click 'Edit Info'.
Scroll down to the section called 'Sympathy gifts' and select 'Contribution to a personal cause' if you'd like donations to be made to a personal account or 'Contribution to a nonprofit' if you'd prefer donations be made to a charity in memory of your loved one.
After you've finished filling out the information, scroll to the bottom of the page and click 'Update Website' to make your memorial fundraiser public!