Set Your Options
Navigate to Home -> Options -> Donation Manager and set all options to what you want.
Make sure the PayPal Primary Account Email option is set to a valid PayPal account.
If you don't see this option set it in Users -> List User Upgrades as it is currently using the same option field.
Create Your First Goal
Navigate to Applications -> Create New Goal and fill out your first goal.
Remember if you want the goal to be displayed in the sidebar to check the featured option.
Set Correct Permissions
Nothing will be shown yet as permissions have yet to be set.
Navigate to Users -> User Group Permissions -> Registered (or whatever group you want the permissions set on) and scroll down to the Donation Permissions group.
Select what you want your users to be able to see and then save. Now everything should be working, it is recommended to test things yourself with a small donation.