Changing the location of an entry works similar to changing date of an entry (backdating.
In iOS, this can be done in two ways:
a) From Editor: To invoke this function, click on the Location icon in the Toolbar.
In the popup, you will see an option to either remove the location or search and pick a new location.
b) From Today/Day Trail: There is another way to create entries with historical information through the day trail view. To invoke this function, navigate to the Today view andpick a day where you have Day trails available. Then, click on the needed location pin that appears on the Day Trail.
Note: Day trails are turned off by default for privacy reasons so you need to turn on this feature from Settings/Personalize/Track Places Visited.
On the Mac app, this option resides only in the Editor. This function can be invoked by clicking the location name as illustrated in the below screenshot.