Assigning location to question is optional. Only set location when asking this question does not make sense anywhere else, when question is location specific.
Location specific question is for example following:
Nearby is a statue. Shoot a photo of your team and a statue.
You should assign a location to it. You can use the question in different games, but it should always be in this location.
General task would be following:
Shoot a photo of your team where nobody touches the ground.
You can still assign a location to it when creating a game, so it can activate in different locations in different games.
You can set a location by:
a) typing in an address
b) clicking on a map to point the right place
c) pasting in exact coordinates in degrees (dd,dddddd)
After you have set the location using any of these means you can move the question around.
Radius is an area where question actually activates. Default is 10 meters and in most cases this should be alright. If you make the radius smaller the question becomes harder to activate because of GPS inaccuracy, but it opens closer to the wanted location. Bigger radius is easier to activate, but it opens in a less controllable way.
Question that has radius of 3 meters or less are very hard to open in real world.
Changing location later
In case you need to change the location of the location specific question later you need to open the question for editing. Location will be changed in all the games this question is present.
In case you delete location from a question that was location specific and was added in games the question in games will preserve their locations but are now considered not location specific (i.e. location is set by the game)
In case a location is added to a question that is used in games and did not have location, the location will be overwritten in all the games!