Manipulating Vertices in Metal

Hi There,

I have a 3D mesh, now it is an obj file. I want to import it into my program and be able to transform one or a group of vertices.

Let's say, i have a human model and I want to lengthen the arms. Which means I need to position the vertices in the arm, separate to the body. I also want to position the coordinates in the UV 2D speie on the texture image. Please help.