Hi there! Firstly, let me assure you that it is NOT a stupid question at all.
The reason that many people suggest using the SystemRescueCD to install Gentoo is that it is Gentoo-based, more up-to-date than the official releases, and that Gentoo can be installed from within any Linux environment that has a console.
Basically, you will just download the System Rescue CD
, burn it to a disc, boot it, and install Gentoo as normal, using the Gentoo Handbook
If you have any questions, comments, or concerns regarding the installation process, or more macrocosmically, Gentoo as a whole, please feel free to post them here or on the Gentoo fora.