Go to options > hotkeys. Right click to add a new hotkey. Choose hotkey trigger, for example alt+O. In the "Text for Search Edit Box" field, enter this: gooptions
You can also make a shorter alias, which I find easier to remember compared to hotkey combinations. Create a new alias. Set the trigger text to "opt" and in the results box enter "dosearch gooptions". You can now type "opt" in FARR to immediately open the options.