show sub_menu like sys_menu in tentacle theme

[stardust]

Hi, I've been trying to make a link that when you hover, it shows the links in sub_menu. I know this can be done with sys_menu (in themes like Tentacle, Project Vii, etc); but how can you get it for sub_menu too?

my practice layout: http://www.itvxq.net/cpg

sys_menu is under "MEMBERS" & I want sub_menu to be under "GALLERY". I have no idea how to code that...Right now some links for sub_menu are in the main navigation but I will change those once I can get sub_menu under one link. Can anyone help me with this?