It's already built into your boat
You can find it on this website at: http://www.odayowners.com/manuals/25mast/oday25mast.pdfYou'll need a piece of 1/4" line to run from the shroud triangles to the boom end.Attach the main halyard eye to the boom end and cleat the bitter end at halyard winch or one of the cleats near the mast base.If the gooseneck is still running in the internal groove, (as opposed to a short section of external track), slide the gooseneck down to the bottom of the mast. Otherwise you'll need to find a way to attach the gooseneck at the mast base.The standard mainsheet tackle will provide enough effort to pull down the boom/raise the mast.After you have done it a few times with help and know what to look for, you can do it singlehanded.