Multiple sizes of same font (for mobile)

Did some searching, have not found adequate answer, but this must be something obvious I’m missing: I need to have several different font sizes, because ‘mobile’ does not support dynamic font sizing, right? So, if I understand correctly, my option is to have several fixed-sized fonts, and choose the best one for the size device I’m running on.
The question is, how do I get different sized fonts? That is, for example, I import Arial.ttf. It gives me the option for font size. Now I can use that font in my GUI. But I ALSO need several OTHER sizes of Arial. Do I need to use different copies of Arial.ttf or something?
Again, it must be something obvious I’m missing.

Yes, you need to duplicate the font and import the duplicates at different sizes. Either that, or use one copy and import at the highest resolution, and then scale the text down for lower res screens. Obviously you wouldn’t have pixel-perfect fonts in that case, but in my experience it looks fine. (Scaling up, of course, is not recommended.)