If you stand at the back of the trainer, the adaptor on the left need to be taken out and swopped with the one for boost. The one that was given to you i assume.
I interchange both my road bike and my 12 Speed MTB on the trainer. Yes you need to put in the left triangle adapter, then you unscrew the one on the right that is in the cassette (meant for the road bike) and you screw in the one for the MTB.
