Something like this:
Cable the Cluster Switches to each other.
Configure mgmt, patch to the correct firmware / install the RCF files.
Make sure the 2750 and A400 are on the same ontap version.
Whichever pair is 01/02 is really up to you, i would probably put the A400 as 01 02 and the 2750 as 03 04
Connect the cluster ports/mgmt ports etc on the A400 as per the docs.
Setup the cluster as per the docks.
When the 2 node is healthy, cable up and join the other pair to the cluster.
After that, configure disks/aggrs/networking/etc.
Run Active IQ config advisor
Lastly, test failover giveback on each HA pair before going prod.