There are two location settings to consider.
First of all you can show others where you're from on your profile. Simply edit your profile and add where you live (it's right next to where you describe your faith, name and age). This is an optional free text field and can be used to tell people which town, city, region or part of the country you're from. Be as general or specific as you like, or leave it blank.
Secondly, the SALT app needs to know where you physically are to show you the correct stories and also to ensure your profile is shown to other people (don't worry - your exact location isn't shown to other people). The default setting is for SALT to use GPS to automatically work out where you are and show you people near you. If you'd rather fix your location to a set point, simply toggle this setting off, and move the pin on the map. This is helpful if you're moving a lot between a few different locations. All of this is found in the Location section in Settings.