Connecting tub drain to main drain

I was smart enough to pay for new plumbing re-route in remodeling bathroom. Had to add in a contractor as going through joists was necessary (upstairs bathroom). I have now purchased tub and tub drain kit. I see a 2 inch cap on the main drain. I "think" what I need to connect the tub drain and the main drain is a flexible t-fitting. Is there anything else necessary? And to secure all these together (all plastic) do I use the stuff in the bottle with the applicator? I really want to diy as much of this job as I can.

If the plumber did you any favors, he didn't glue the trap so that you could position it properly to connect. Do NOT use a flexible connection. A picture of what you have might make it easier to give a recommendation on how to proceed.