To connect the racks you need to:-

Stand the racks to be connected side by side and face the back of these racks.
Remove the 4 existing nails, 2 either side of the space to be connected, in 3 separate places strategically within the 12 spaces to be connected i.e. rows 1, 6, and 12
Position the long steel strips to ’join’ the two racks and spaces and refix with the new nails provided.
When steps 1 to 3 are complete, simply tap the small steel connecting strips into place at the front of the rack.
Fix the rack to the wall with either: a) screws directly into the wall through the predrilled holes in the 45 degrees angled steel fixing plates at the back of the rack, or b) by screwing the rack to horizontal wooden battens positioned on the wall in line with the predrilled holes in the steel fixing plates.
N.B. If the batten system is used, then steps 1 to 4 above are not needed, as the racks simply need to be fixed to the battens with an appropriate gap to allow the connecting strips to be tapped home.