Here are the things to check
1. Make sure that you've got the film speed dial set correctly in front. There's not a "100" setting, so set it for either "75" or "150".
2. Make sure that the exposure compensation dial (the black/white dial) is set correctly. Start in the center, half way between white and black. If you've set the film speed dial to 75, cheat the dial a little dark, and vice versa if you've set the film speed to 150.
3. Set the scene selector to the correct setting. In this case, "outdoors without flash"
4. VERY IMPORTANT: make sure you are getting full exposure from the shutter. Don't just push the red shutter button: squeeze it down and hold it! Those cameras can have a maximum exposure time of as long as 5 seconds, but if you let go of the button the shutter will close even if the proper exposure has not been reached. Always hold the shutter button down for a second or two every time you take a picture - in low light you will hear the shutter open and close.
5. Lastly, the light sensors drift over time, so each camera will meter a little differently. After you've shot with a few packs of film, you might find that your camera tends to consistently over or under expose. Just adjust the light/dark dial accordingly.
good luck! They are indeed great cameras.