Hi usiddiqi,
The only place in Dubai to get your fingerprints done is at the main CID office, located next to Al Mulla Plaza on the way to Sharjah. Just go to them, explain at the reception that you need your fingerprints for FBI in USA for immigration to canada.
They will ask you to pay the fees of AED 110. Once you pay it, take the receipt immediately to the section where the fingerprints are done, get your fingerprints scanned. They will then guide you to an office inside a building where you can pick up your original finger print. They are very helpful and you will not have any challenge in getting this done.
They will not do it on the FBI form that is available to download on the FBI website. You will only get it on their form, which is fine and is accepted by FBI, cause I did mine and it worked out fine.
Only important thing, make sure that you clearly mention you need your fingerprint, cause otherwise, they assume you need a police clearance certificate for Canada and will proces that as since the PCC also costs AED 110.
All the best !