I'm new to coding so am struggling a bit to know what code needs to go where.

I have created 2 galleries and saved them in separate folders, where do I load the files in these directories to on my website?
What code do I have to put in my main website page to show the headers for the 2 galleries and then display the gallery on the same page when chosen?

I'm getting quite confused about what code needs to be in the website page header and body, and then what to do with the files (including html js and xml files for the two galleries).

Any help you can give would be greatly appreciated.
Thank you