Hi there, all basic attributes associated with the towers are set through the ‘Tower Data Array’ in BP_GameInstance class. So for example, if you want to change the range of the Machine Gun Tower, you can expand the array, select the element associated with the same, & then modify the ‘Range’ parameter as shown below:
That should change the range of the tower, next time you spawn it within a level. The size of the range display ring will also get updated as per the new modifications.