I looked in the discussion for like 30+ mins, and I asked friends, but I just didn't find an answer...
There is a specific asset you can drag onto your map, DA_Portal_1600m or so in the Core plugin. Place it in network edit mode, hook up a piece of track to that and it should work right away.
OK, create a normal go to instruction and click in the portal. It should be converted to a enter portal instruction.
Found it, you need to go to the height menu, and then select the connection point, and set the Portal Name at the down right
"Unable to find path for ICE at instruction 1, waypoint 1 (Unknown or multiple errors, check output log for further info) 1. Leave portal ICE" now I have this error :/
If you already have tracks laid and connected to the portal, and think it should be working and then it doesn't, you might have to clear and re-fill your signals unfortunately.
I've seen that error when I told a train that's already in the vault to enter a portal, or a train that's on the map to leave one.