How to work with @2x and @3x?

Question

iOS

Good day.
It just so happened that I had to take up a new business for myself, namely design for iOS.
I had no experience with this before, except that sometimes I used Photoshop for personal purposes, I seem to know it well.
For all questions, the answers are in Google. But... Not without a but. Here I could not comprehend the picture completely. I read articles from Rambler on Habré, everything was beautifully and clearly stated on this subject, it
seems like we are starting from the permission of the five. Okay, no problem with that, 5 uses @2x,
8+ uses 3x, got it. So the question is, where to get @ 3x? From under five? Or transfer the design to 8+ artboards and export @3x from there? How should the slicing/export process take place in general?
Since my programmer is the same as I am a designer, he cannot clearly tell me in what form he needs design, both are still learning.
I will not refuse general advice on the organization of work in this matter.

Answer 1

You add elements to the Assets panel for unloading
File - Export - Export For Screens and on the Assets tab, in the Format column, click Add Scale