Question re FCC Linux Dual Boot instructions - Gentoo

I would like to try Linux, I will need to know it soon enough. I was following the instructions here from the Free Code Camp article on Dual Boot Any Linux Distribution with Windows.

I chose Gentoo as the distribution I wanted, as my main objective is to learn usage of operating systems rather than just having an alternate OS to Windows or MacOS. I have created a boot flash drive with Gentoo on it using Fedora Media Writer, and have created two partitions on my hard drive. But I was in tandem reading the Gentoo docs, and it is a bit unclear on partitions. It seems that Gentoo may create partitions as part of the installation process, instead of me creating them manually in advance. But I’m not 100% sure on that.
Has anyone here installed Gentoo as a dual boot? Does it actually create partitions during its installation, in which case I should undo my manually created ones so I have the space? Or have I read that wrong?