Go to the map screen and move the cursor to the required location. Select ENTER, you will get a screen with GO at the bottom. (If you want to go there but not create a waypoint select ENTER again). Select MENU. You will be offered the option to create a waypoint. Select ENTER to create the waypoint then MENU if you wish to edit information. Back out with QUIT till you see the map and continue to create wayoints.
On my gpsmap 62s (firmware version 3.0) using MARK creates waypoints at the current location which you have to move. This procedure is time consuming particularly if you wish to create a series at a distant location.
TLDR: map-screen/enter/menu/enter/menu/quit