Twilight check-in is between 3:30pm and 9pm
Boading starts about an hour before take-off time, but I would make you way into the departure lounge a while before this to allow for any delay in the security check.
When you check in they will tell you the time you have to be at the gate.
There are also loads of shops and eating places in the departure lounge, so you may want to allow some time for some shopping or a nice breakfast
Here the baggage allowance details:
Hand luggage
You are allowed to carry one piece of hand luggage onto the plane. This must be able to fit under the seat in front of you, which means it must not be larger than 23cm x 36cm x 56cm (9in x 14in X 22in) overall and should also not weigh more than 6kg (13lbs).
An infant's carrying basket and food for consumption during the flight will be carried free over and above the baggage allowance, as will a fully collapsible wheelchair and/or a pair of crutches. Both the carrying basket and wheelchair will normally be carried in the hold.
Checked in baggage allowance
As well as hand luggage you are allowed to check in the following:
Transatlantic/Lagos
Two pieces of luggage per passenger each weighing up to 32kg (70lbs). When added together, the three dimensions of any piece of luggage must not exceed 158cm (62in).