On Linux, there is no easy way to do this. Okay, not that easy. Like TeamViewer is not avaliable there. Anyway, you can use many ways to achieve this.
Graphical help: VNC or krfb or Gnome desktop sharing
"Console" help (this is what everyone use for servers, for desktop PCs, whatever. Best "tool" (feature?) on Linux: SSH (First this may seem alien, but once you get used to it, this is the very first utility which comes when you want to remote assist. Okay you can't pester the graphical environment with this.)
(For both, you need an open port on the other side and have to know the other side's IP.)