I was using a Pixel 2, but the list of well documented phones is available:

https://lineage.microg.org/

It's pretty simple if your phone is supported. You enable developer mode, enable USB debugging, download the image, and run a couple ADB commands. For me it was:

fastboot flashing unlock

fastboot update image.zip

And that was it.

>What phone did you load LineageOS on? Do you know of any guides for it?

Not GP, but I'd been using LineageOS on my HTC OneMax. I like it a lot.

Here's a list of supported devices:

https://wiki.lineageos.org/devices/

Click through the links on the above page for install guides.