Sadly, they completely changed their help files. The files I used were really clear about installation, but now I can't find them. You might ask where they moved those files in the forum, here: https://www.phpbb.com/community/viewforum.php?f=481
Actually, the styles installation is simple. Be sure you pick a compatible style for your forum version. For example, if you picked 3.1.6 as your version, then all the styles in THIS forum (by Arty) work. Here's the extension database
, but you have to select the proper phpBB version in the 'All Branches' toggle at far right, and then select the 'Styles' at far left, to see what's available for your version.
There's a huge difference between 3.1.x and 3.0.x, but little if any difference between one 3.1.x and the next, except that there is a bigger difference between 3.1.3 and later (3.1.3 and later are compatible with each other). BACK UP your entire board before you add any extensions, just in case adding them borks your board. Each extension should contain its own instructions for how you add it, to what folder, etc.
Trick is to download, then FTP upload those styles in the right folder, which is your public directory root, forumname, 'styles'. Once they are uploaded there, you'll easily be able to install them via the Administrator Control Panel 'Customize' tab, which has a 'Styles' option in the left frame. You just click on 'Install Styles' and it does, then click on 'Styles' and make any changes you want.
However, the kind of changes I talked about on the video have no help files. I just guessed by looking in each style for the logo file, then loaded it up in Microsoft Works Digital Image and changed the image by adding 'FrankForum', then saved it with the same name. I also searched in the css style sheets for the 'font' and in some cases changed the font size percentages (which show up early in search).
Of course, you'd never do that preceding paragraph without first copying your original images and stylesheets. What I did was to copy then rename the file then rename the original with ORIG appended to the name (before the period), and then rename the changed version to the name of the original file.
Hope this helps!