Give plenty of 'lead string' (to the right of the butterfly) before starting the actual warp. I wrap the string around the frame at least three times then knot the thread as close to the end of the string as possible. You will thank yourself for the extra string later when this tail needs to be hidden inside or knotted off.
Sometimes I use a little tape to keep things stable. It is also useful for keeping the strings separate and in order at the beginning -- as you will see later. Masking tape works best for this (I'm using a narrow 'artist's tape'.)
Standing on a chair to warp the loom. The string will progress in one direction in wide loops around the frame. The goal is seven warp strings in the front for a belt. Make sure you don't cross your strings anywhere, or loop around any other horizontal bars that may be in your frame (see pic). The warp (string) should be a continuous loop or 'O' -- if the warp (string) makes a 'figure 8' anywhere, that is not correct!
Tying off the Warp, the same way you tied the beginning string to the frame -- leave lots of extra string! Note the tape on the warp strings to keep them separate and in order from right to left.