Ok, it's not hard to program coordinates into you etrex. Once youre powered up, go to the menu page, which lists these options: "Mark," "Find," "Routes," "Tracks," "Setup," and "Accessories."
Use the toggle on the front of the device and toggle to "Mark." Push the toggle switch in and release. Now you should have a page with a man holding a flag. Inside the flag you should see a dot & a number. Use the toggle switch to go to the dot and push the toggle switch in and release again. Now scroll up to identify what it is you want to mark (ie. geocache, building, etc.) (pushing in & releasing the toggle switch is like hitting the Enter key on your computer). Now toggle to the number on that flag and push the toggle switch in again. No you can move your cursor around and give your new waypoint a name.
Once that part is done, toggle down to the coordinates and click on them. You should now be able to enter new coordinates. Enter them just as they appear on the web-page. Once that is done, just toggle down to OK and click on it. Your waypoint is now programed into your GPS.
When at the site of a geocache, power up and go to the same menu as described in paragraph 1 above. This time, click on "Find." Follow the prompts and click on the waypoint you want to search for, then click on "Goto" on the bottom and youre on your way. I hope this helps. Happy hunting!