In BaseCamp, click on the New, Waypoint option and place a waypoint anywhere on the map. Now select that waypoint in the My Collection tab, go to properties and change the coordinates/name to what you need. Do that for every point you have on your list. Once the are entered in BaseCamp, highlight them (left mouse click with CTRL) then while holding CTRL right click, select send and if your GPS is connected, you'll be able to send them to the GPS.
A refinement to SARLAB's answer is to use Ctrl-T (View->Recenter Map To). This will bring up a dialog where you can enter your coordinates and create a waypoint. With your GPS device, you also have the option of creating these waypoints directly on the device by having the device selected when you do the above.
If you have a lot of these to send, another option you can explore is to look for tools that will convert a CSV or tab-limited file with lat/lon to GPX.
