Solution
You can wear your custom designs from the custom design menu and put them in the custom design section in Able Sisters to share with other villagers/players, I don't think you can make them into normal clothes items
Actually, very early in the game, you can just select one design in your menu, from anywhere, and you have an option to "wear" it:
as a shirt, as a little hat or as an umbrella (only outside).
as a shirt, as a little hat or as an umbrella (only outside).
