Any resources/tips/help for using texture files on not square uv map islands?

im having some trouble using texture files and connecting them to uv maps’s islands which arent square shaped like the textures are.

are there any tips, help and/or resources to learn this?

I know the basics on painting the base models but am looking to use textures but they are square shaped and my uv map islands are not perfectly square.

I would recommend using square UV maps exclusively, it will be much easier to remap your UVs to a standard 0-1 space than try and get your texturea to work with a nonstandard UV space

my uv map is the square but the islands are what i’m asking about. sorry for the confusion.

Quadrify your islands!
I believe TexTools UV editor has that function called Rectify…
I prefer to use UV-Squares as it works very well…

None will work well if the mesh is triangulated, so first it needs to be run through Face > Tris to Quads or using a re-mesher…