Welcome to the forum and congratulations on your new sailboat!!
Based on the 461 manual page 32 attached you have a Z-Spar Z901 furling mast and should have 2 inspection ports on the mast per the Z-Spar In-mast Furling Guide attached. Suggest contacing Z-Spar
Z Spars International (z-spars.com) for a manual with diagrams to aid mainsail installation
From the Z-Spar In-mast Furling Guide: Installing the sail: Open both sets of inspection covers (C) by removing the top screw and loosening the lower one. Moving the cover sideways will reveal the sail entry slot cut in the furling extrusion (B). Feed the head of the sail through the mast slot and into the sail entry slot. Lower the main halyard to allow the shackle on the top swivel (A) to be attached to the strap sewn into the head of the sail, using an Allen (hex) key. Continue to feed the sail into the slot whilst the main halyard is being hoisted. Do not attempt this with the wind astern. The task is best attempted in little or no wind. Connect the bottom strap on the sail luff to the base of the furling extrusion with the shackle provided, by gaining access through the lower inspection ports. This tack shackle also connects the furling extrusion to the furling drum. Refit inspection hatches. Complete the installation by applying moderate tension to the main halyard