Hi I am new to Sabayon too and I decided to get easy tag because I use it as well and wanted to install it. First program I am installing in Sabayon by the way and I ran Portato (which you need to be root) then searched for easytag and checked all the empty boxes and clicked emerge (which I assumed was install) then it went to the next tab and I chose emerge again then it opened the console and I saw it do its thing and it took a few minutes when it got to easytag when it was installing it but it finished with no errors. I then found it in the menu and clicked on it and it loaded fine and ran fine.
I did this on Sabayon 3.4a by the way.
That was my experience hope it helps.
Anything that pertains to Portage