TL; DRAnywhere! Though, if you're looking to follow common wisdom, you put a fuzz pedal at the start of your chain. Fuzz pedals commonly can affect other guitar pedals in your chain in terms of making unwanted noise, so usually they're placed early with other drive and dirt pedals, but they can go anywhere in your chain.
Long Answer:
Alright, one of the biggest questions constantly plaguing fuzz pedal enthusiasts: Where do you put your fuzz? While it is true that you can put any number of pedals in any order, there is a generally agreed upon wisdom that you put dirt pedals at the start of your chain. This includes your fuzz pedal. Traditionally, you want your drive pedals – your overdrive, your distortion, your fuzz – before any time-based effects like delays and choruses. You plug into your dirt pedals first before plugging into delays, modulations, and reverbs.
You can put a fuzz pedal anywhere in your chain, just as you could any other type of pedal. However, fuzz pedals perform their best in the front of the chain due to their design. Fuzz pedals put later in the chain, after a bunch of other pedals, might cause unwanted noise by amplifying sounds they wouldn't pick up by being as close to the start of your signal chain as possible.
