Miche hubs are not super common, so I thought I’d do a write up on changing the freehub. I’m changing my bike from a Shimano freehub to Campagnolo. I’ll assume you have your wheel already removed.
Loosen the bearing preload, it’s the tiny little allen key bolt on the cap on the non-drive side.
Each end of the axle has a cap, the cap has a hole for a 5mm allen wrench. Put a wrench in each side. One is to hold the axle from spinning while you move the other clockwise. The axle has reverse threads. Without too much effort the cap should break loose so you can unscrew it.
Once the cap is off you can pull the axle out of the hub.
Remove the free hub from the axle.
You might want to clean and grease the axle. Now install your new freehub on the axle and then the bushing that comes with the freehub. Be careful greasing the pawls and splines. If you use a thick grease, it could impede the pawls from moving. Same could happen if you use too much grease.
Install the axle onto your rear hub. You will have to push the pawls in to get the freehub to go in. Next you put the cap on the end and tighten. Again, reverse threads, so tighten is counterclockwise. I just did it pretty snug, I saw 5nm suggested for a different brand.