The Arrival Yaw is just the rotation that the character spawns in the map in degrees. You'll have to place the destination position (XYZ) of the portal/gate in the location you are wanting to get your character to spawn in the right location.
This is what I do to get that spawn position accurate:
Grab a small object from the object group lists. It could be anything, it doesn't really matter, but a rock might be the easiest to visualize. Move it to where you want the character to spawn in at.
Go to the 'Controls' tab while the object is still selected and make note of the X, Y, and Z positions. You can either write them down or screenshot it and open the picture, whichever is easier for you ^^
After you have the coordinates jotted down, delete the object you placed down.
If it's a portal to and from the Cape, you will need to change the Destination Position (XYZ) under the 'Map' tab.
If it is a gate you are working with between two maps that are your own, you will need to edit the Destination Position (XYZ) under the 'Objects' tab. If you're working with a gate, make sure it is selected by selecting the Gate type under the 'Controls' tab and then going back to the 'Objects' tab to adjust the position
