Placing designs in mockups makes it look like the apps and products are real, even though they're just UI concepts! Here's a YouTube tutorial, and a how-to guide on how to place UI design in a mockup.
This is a review of the Affinity Designer on the iPad Pro for UX/UI Design. What features does the program have and can you use it as your primary design tools?
What are the best books to learn UX/UI design for beginners? Here are my 4 best book recommendations. These are the ones I used myself when I first started learning.