Geocoding is the process of converting physical addresses (for example, 13 Rademaker Road, New Jersey 07001) into Latitude / Longitude coordinates (e.g. Latitude: 15.23444, Longitude: 62.23322). This is essential because the location of the sales rep on the map is defined by the Latitude / Longitude so if the geocoding process fails, your sales rep locator will not be able to show the sales rep on the map.
When you perform a bulk upload, you will receive an email once the geocoding process has finished. Depending on how many locations you have, this could take from a few second for less than 100 locations to upwards of 30 minutes if you have thousands of locations. Don't worry, this is a once-off process that happens when you first perform your sales rep list upload.
The email will give you a list of sales rep addresses that have failed geocoding. You will need to click on each of the sales rep links in the email to manually adjust the sales rep location using the map. However, if all your locations failed to be geocoded this often indicates a problem in the address information that you have provided so it's worth checking how this was imported and adjusting if necessary. This article gives more information on common upload problems.