How do u conect vertices?, i forgot. Sorry i ask stupid questions.
In edit mode the FKEY will join and 2 vertices to make an edge or make a face from and 3 or 4 selected vertices.
or if you mean weld them, select 2 vertices and press alt M.
You can also select the vertices, snap them to center with shift-s and then remove doubles from withing the W-key menu… it’s all the same…