Just Relax.
1. Keep the letter for Biometric received from HO
2. Keep the Biometric enrollment number. I got my enrollment done by calling a phone number and they gave me the a number. That number you need to write in a square box which is there in you letter received from HO
3. Reach half an hour before your appointment. I went to Croydon and they did not allow me to enter as I was 1 hour before time. I was allowed to enter just half an hour before the appointment time.Looks like this is their way yo manage traffic
4. Once you enter they will do your baggage screening (like done in airport)
5. You will be guided to a counter where you will have to show your biometric letter. At that counter they will give you a token number and will guide you to a hall (this hall will have many counters)
6. Once inside you will have to keep your ears open and listen when your token number will be called at a specific time. Listen carefully to the counter you are called at and go to the counter
7. Once you are at the counter they will ask you couple of question like is you biometric taken before by a UK authority. Basically there is a form with 2-3 question that they fill and ask you to sign
8. After that your photo and finger prints will be taken
9. You will be asked to go and wait
10. After some time your token will be again called and you have to go to another counter
11. In my case the officer just told me that your biometric is completed and you are free to go
Thats it, very simple, in my case I was out in about 75 minutes.This was the procedure at Croydon office and I am sure they must be following similar process in all other offices as well.
Keep some snacks and water as you are going with a kid.
They did not ask for my photo ID, but just keep yours and do not bother about your kids photo ID.
Good Luck and Best Wishes.
Cheers,
Jacob.