The best description I found with a not so short Google was buried in https://www.redhat.com/sysadmin/fzf-linux-fuzzy-finder but the workflow is I hit ctrl-R (in bash, but there's bindings for other shells), I type out part of the command I know is in my history, and fzf will grep history for commands that match via its fuzzy search algorithm. So if I remember running something that involved a file called something in a log dir, I type /log/, and it interactively lets me search. I remembered I was using awk with the log file, so I can add "awk" to the existing search), and then I use the up arrow to select it and hit enter. at which point it's in my command buffer waiting for me to either hit enter again or edit the command and then hit enter.

Might sound complex written out like that, but I promise it's worth the investment to set it up and read the manual.