Yep very little is automatic with Garmin, so "hope" doesn't work unfortunately

They aren't user friendly at all as their main focus is on battery efficiency and plenty of stats for athletes etc.
I just tried adding the Orbea one to my watch (Fenix 5X+) and it worked ok, but it's a technical process and tricky if you're not familiar with doing it regularly. These are the steps you should be looking to go through:
- Choose the activity you want to add the data field to (or create a new activity)
- Open the settings for the activity (for me it is hold left middle button while the activity is selected)
- Go to the "data screens" section of the settings
- Add a new data screen (last option in the list) - only gets created once you go through all the next stages (so don't back out). You can always edit it again later too.
- Choose Custom Data
- Choose the layout to only have one data field on the data screen
- Choose the Orbea RS data field as the one you want to use (it will be listed under ConnectIQ fields)
- Move the data screen up or down in the list (or leave it where it is ... this step is just confusing ... press select button top right and should be added finally)
For me after doing this, that activity then says "Orbea RS Trial Is Active" and going to the correct data screen it says "Unlock in Garmin IQ Store" - but it will hopefully work for you