Usually fairly straightforward - click on the yellow imdb logo beside the film title and date - that should open up a page about the film. Look under the Details sub-head - there's often a line about Filming Locations and open that up to see contents. If there's nothing on locations, there can be clues from nationality of film producers etc. But as ever, there are holes in the info (no entry or incomplete listing - we often discover through imcdb's captures additional locations to those presented by imdb) or multi-national locations (eg Bond films etc) or films which pretend to be in a different country etc etc, so things can get complicated.