Step 1: Install texMemo Latex Class

The first step is to install your Latex class. Do this by downloading the bundle of Latex class files from this link: http://oak-tree.us/stuff/LyX/texMemo.zip

Then copy texMemo.cls to ~/Library/texmf/tex/latex/lyx (you may have to make this directory).

Now run texhash (you'll probably have to run sudo texhash). This will update your Latex databases so that they know about your new Latex class.

Step 2: Install texMemo LyX Layout

Now download the bundle of LyX layout files from this link: http://oak-tree.us/stuff/LyX/texMemo-LyX.zip

Then copy texMemo.layout to ~/Library/Application Data/LyX-2.0/layouts.

Now open LyX and click LyX > Reconfigure in the top menu bar. This should update your Lyx database so it knows about your new Lyx layout.

Now you can use the class. Examples are included in the zip files, so use those!