Here's a few resources that may help you get started:
In-house Video Tutorials for Affinity Designer and Affinity Photo
The Affinity Designer Workbook - Affinity Designer’s Official Guide
The Help file (menu Help ▸ AffinityDesigner/Photo Help) covers extensively all features/tools of the each program, don't overlook it.
I’ve also compiled a list of other learning resources here, including third party Books, Training Courses and Tutorials
If you have any questions or issues, feel free to ask here in the forums. There's always users and staff willing to help.