Hello,
In the F5 GUI, there are field names listed in the help tab on the left.
I find it easier to search for request logging on the internet. F5 documentation on request logging, though I am not sure about a step-by-step doc.
It is really not complicated, but I have found the GUI configuration is buggy, at least in the version I was using. If you configure a Request Logging profile in the GUI, then list it in the CLI, you will know if there is a problem. If configured in the GUI, the F5 will save line breaks in the config if the fields listed do not fit on a single line. To work around this, I copy the config, remove the line breaks and merge the profile back into the CLI.