Steam on Debian 7

I'm trying to set-up an "arcade" system with steam with Debian.
I've been looking through all the internet and I can't find any info regarding all this:

First of all:
I need to add the architecture for 64bits system is
dpkg --add-architecture i386
Thing is .. IT doesn't do ANYTHING.


After this it asks me for some dependencies

Package jockey-common needs to be installed
Package xterm needs to be installed
Package libgl1-mesa-dri:i386 needs to be installed
Package libgl1-mesa-glx:i386 needs to be installed
Package libc6:i386 needs to be installed

What am I doing wrong?
After "installing them" it asks me over and over again to install them.
I gotta say I'm no expert on Debian, or Ubuntu overall. But this is driving me crazy.