It is a lot easier to modify WordPress templates when it is done offline or when WordPress is installed locally on your computer. I thought I wouldn’t need to resort to a locally installed WP but the last time I was tinkering with a theme, it took ages for the updates to load on my test site!
Installation is easy, in fact, there are tons of guidelines you can Google out there. But this is what I have used along with setting up ‘xampp’ on a Mac. Try it out!