Why can't I install ".deb" files?

[Shodex]

I'm new to LXDE, I have some knowledge of Linux through Ubuntu but I'm still mostly a Windows user. I'm trying to install Xchat and Google Chrome, but when I double click the ".deb" files it asks me what I want to open them with, instead of just opening. I'm sure there's a very simple solution to this but like I said, I'm new.

How do I open/install ".deb" files in LXDE (I'm using the Gnome environment, by the way)?

[seppalta]

It is easiest to install from the Synaptic Repository. The applications you mentioned should be in there. For directly installing a .deb files you need either gdebi or dpkg, again both can be installed via Sy.
naptic. See http://douwil7.100webspace.net/linux/Tuning.html#7 for more information.

[Shodex]

Thanks a bunch, that was easy.

[pheobe green]

Thanks a bunch, that was easy.

I also do not know, can you tell me?