You will have to clear immigration as you are entering the schengen area, but it’s usually very quick and painless. Remember to follow “transit” and or connecting flights. You will then stay in the transit area and still be airside.
The lounge is by lift or stairs near the transit desks and security lines for gates A1-10.
They have showers and even en-suite guest rooms if your stay is a long one. Enjoy it!