Once you've installed the new seals (I think they'll remain in the master cylinder when you pull the reservoir), "lubricate" the nipples on the bottom of the reservoir with a little brake fluid and push the reservoir back in.

Before you attempt this, get a turkey baster and suck as much of the fluid as you can out of the reservoir. If married, don't get caught with the significant other's baster, and toss it in the garbage when you're done.

Don't attempt to reuse the fluid - replace with brand new stuff from a newly unsealed bottle. DO NOT make the same mistake I did about 2 years ago - using fluid from a bottle on the shelf in the garage for years - 2+ weeks after using the fluid, the master cylinder went south.