Are there currently, or will there be, any other IAPs on the same VLAN where the 387s are going? Additionally, is the plan to use the backhaul to carry other IAPs of the same VC between both sides over the mesh? If so, post that here as the below steps will change.
For a single VC, assuming the above does NOT apply, the easiest thing to do is listed below, and provides the best check to ensure everything is good before hanging them up
1. Plug them both in to the network and bring them up, update the firmware and DRT
2. Define the wired port profile as needed (access, trunk, VLANs, etc)
3. Disable extended SSID (not really necessary but I do it anyway)
4. Before rebooting, enable eth0 bridging on the mesh point only
5. Reboot the two, and after the point goes offline, move it to a power injector or a separate POE switch not connected to the same L2 the portal is on.
6. Give it 10min or so to let it all reboot (watching and waiting seems to make it take forever), verify the portal and point are up in the VC.
7. Test/verify that the mesh backhaul is working and carrying whatever traffic or VLANs you configured
Easiest way to verify since we don't have mesh in the GUI yet will be to log in to the portal and point and run 'show ap mesh links' and 'show ap mesh neighbors'. When staging, it's common that that the link won't run at full speed, when the APs are too close together.