Congratulations on the purchase of your new haft.
The primary method of retention should be a steel pin secured through a pre drilled hole (slightly undersized) to the pin. The pin should be peened from both sides to keep it secure. The pin is typically set across 180 degrees from the primary impact vector.
We strongly suggest the minimum method for securing your weapon head to the haft is to contour the oversided head area of the haft to fit your weapon with just enough room for some epoxy, in addition to the peened pin. The epoxy will aid in retention. Sometimes a few thin hardwood wedges can further help to further secure the fit. These should be liberally coated with epoxy and gently hammered into any gap between the haft and the weapon head. Once cured (usually 24 hours), they should be trimmed to a neat appearance.
It is typical to have ¼” to ½” of the haft protruding from the top of the weapon.
THESE wedges MUST ONLY be used between the haft head and the metal of the weapon as a means of reducing pivot on the pin.
A Wedge must NOT be used as a spreading fulcrum hammered into the top of the haft. This will cause the haft to delaminate or split along the path of the wedge. This is unneeded and super unsafe. It will also VOID any and all warranties, not to mention potentially harm your friends.