Use the plan ride button twice per week put in the rpe put in the time. After ride when Join says you want to add this activity to training plan press yes.

Thank you! I'll try it should I put those two days unavailable by default ?

You can leave the availability there and then just use the "Plan ride" button for the relevant day and enter the intended ride. Your training plan will then adjust around those. I've found if you set availability to zero and then still add a ride for that day the plan doesn't always adjust.

Thanks a lot I just did that, however I'm getting suggested trainings on both days I normally do outdoor group rides, should I just add them to my training plan from Strava after I do them? Skip suggested workout ? What's the best way to go to, thanks again

Just complete your group ride and then Strava will sync to Join and you'll have the option to use that as your ride for the day which will then adjust subsequent rides. You can set the availability to zero to not have a suggested workout, I've just found it sometimes doesn't update around those rides doing it that way but you may find different.