Hold stylus on point on map (where your GPS says you are), choose "Tap Point", choose "Add POI".

The Add POI window opens, touch "Edit Categories", touch "Add". Create a label for your new category. How 'bout "Stuff I can't remember". Make sure Enabled is checked.

"OK" back to the Add POI window and enter a descriptive name for what it is you can't remember. Maybe "Last Night" or "Ishkabibble's", choose your new category and touch "OK".

Because you chose to "enable" your new category, whatever it is you labeled will show up on your map when the area is panned in M/M.

If you want to find your tryst (or whatever, LoL) again in M/M, go to menu; choose "POI", choose "Browse". When the Browse POIs window opens; select "Use GPS Location", select your new category. When the POI List window opens hopefully what you saved will show up, select it, touch "Go to", enjoy another night in Paris.