So unfortunately, with OS10, you stacking is not supported.  I would take a look at "VLT" configuration and see if that suits your needs.  VLT lets you do cross-switch LAGs while maintaining independent control planes.
Hey, So i have got 2 new Dell S5224F Switches that i would like the Stack for LAG. Running OS 10.4.3E I have had a look at the guide but cannot find an answer. I have 2 40G stacking cables plugged into Ports 26 and 27 on both switches. Just looking for the command to run to get these Stacked.  Thanks.
Dell S5224F Stacking