OK - there should be a rope tail on the wire jib halyard. Mine had a long rope section for hoisting that I would disconnect once the jib was hoisted. I then had a shorter, four feet or so, section attached to the same wire loop that the small pulley is attached to. Using this rope, go through the small eyestrap, back up through the pulley on the halyard, and down through the v-jam cleat on the left side of the mast. This is your 3:1 on the jib halyard. You can do this with the long rope tail but it is a lot to thread through everything. For simplicity, you can run the jib halyard straight to the port v-jam cleat on the mast and forget about the purchase. I sailed this way for about a year before I knew any better.

I seem to remember that the v-jam cleat on the starboard side of the mast was used to secure the main halyard (secondary to the fork and ball on the front of the mast).