I'm not sure how new or experienced you are, so bear with me
while I start from scratch...
1. If you are in Cranbrook with a GPS, go to the GPS screen that shows the coordinates of your current location. It should be somewhere that is close to N49 30.779 W115 46.170 as this is the location used by Mapsource for the location of the city.
2. Go to geocaching.com and enter these coordinates on the Hide and Seek a cache page.
3. Look for 3 or 4 caches that are close by and have been found recently. Start with ones that have fewer stars because they're going to be easier and if you're new you may want to read the hint up front so you have greater chance of success.
4. Enter the coordinates of the caches you want to try to find in your GPS as a new waypoint. If you have a GPS that's set up for geocaching you can choose the 'geocache' icon for each waypoint. Head outside and navigate to the closest of the new waypoints that you've entered.
Feel free to come back and ask for more assistance, but if you've only got a day in Cranbrook you may be better off just 'exploring'!