To answer your actual question:
1) completely remove axle and freewheel, if necessary. Keep the nut and cone in place on one side so you have a starting point for reassembly.
2) confirm you have all parts and none are damaged (note: some hubs have different sized bearings and different count on the left and right)
3) clean and grease
4) insert axle from back side to plug the hole just to the race then add a good amount of grease this will help the bearings stay in place. Once you have one side done carefully switch sides with the axle
5) when the second set of bearings are in place gently push the axle the whole way through and install the cone.
You want it to be tight enough that there is no extra play but not so tight that the wheel won’t spin.
I replaced my driver yesterday on a deore hub using this method and my bike is finally up and running. Ready for the season.
Good luck to you.