One man's opinion
Assuming you have slugs on the luff and a bolt rope on the foot, I think you will find it easiest to hoist the luff onto the mast first, and then the foot onto the boom. First, attach the mainsail halyard (it should be on the starboard side) to the head board of the manisail. Then as you haul up the halyard, insert the slugs into the mast sail groove. Do not try to insert the luff bolt rope into the sail groove. Be careful to properly align the slugs, as it is easy to have one or more placed upside down and you will not realize it until you go sailing. After you have inserted the last slug, tighten down the sail stop into the sail groove just above the sail groove opening to hold the mainsail up on the mast. Then lower the mainsail down onto the sail stop. Since, it is very easy to loose the large round nut on the sail stop overboard, an inexpensive replacement is a one half to three quarters inch number 10 phillips pan head screw with a small washer and a wing nut. The wing nut with the screw lightly attached is inserted into the sail groove like a sail stop and the wings on the nut will grab the inside of the sail groove as you tighten the screw. Next, insert the boltrope at the clew into the sail groove on the boom down by the mast. Push and pull the boltrope down along the sail groove for about three feet. Attach a line to the clew which is then brought down to the outer end of the boom. At the outer end of the boom, attach a small block and reeve the line through it and then back down to the mast. Thusly as you pull on the line and the clew, you can feed the bolt rope onto the sail groove. Go carefully as hang ups can occur. Note that you will pull harder on the line attached to the clew as more bolt rope enters the sail groove. To ease the process and make the sail adjust more easily with the outhaul, spray on some of that sail lubricant stuff. I think Harken makes some. Next, secure the tack pin through the mainsail tack grommet onto the boom down by the mast. Next, remove the line attached to the clew and the auxilliary block at the outer end of the boom. Lastly, secure the outhaul to the clew. One last item. The boom may have been left upside down in the fall to prevent dirt entering the sail groove. Make sure it is right side up before starting by having the sailgroove in it face upwards. A better way to keep dirt out is to ship the boom into the cabin in the fall as I do.
