I’m having some trouble with .php files which seem to download when I open them in the browser.
I’ve googled around and have found this is because the server doesn’t know how to parse the file, and that I need to add something to make this work.
I’ve read around and it seems I need to add something to a .htcaccess file, but I’m not sure where this is or where I should create it.
Below is a screenshot of the directories on my server if anyone can help me.

You mean something like
…this should already be in place in the master Apache file (or the appropriate .conf include – in some distributions, configuration directives may be parceled between several configuration files) if PHP is properly installed.