Tell the endo you were referred by your doc as a candidate for HRT. You won't really need to say much after that, other than answering some questions or asking your own. The endo will probably give you an exam and stuff. It can get a little "personal" just FYI. The endo should have further information on what HRT will do to you physically and any of the risks and stuff you need to be aware of. Usually an endo requires approval by your therapist to begin treatment but they can measure your current levels and get a plan put together with you. After getting approval, you will likely need to see your endo again and get your script. IDK if your blood tests were for your current hormone levels. You have to get blood work done a lot for different tests.
I don't remember needing to say very much on my first endo visit. She seemed to know why I was there. It is not typical that people make an apt with one without saying why they're going. Assuming your endo has at least decent bedside manner, they should have everything ready before they step into the room.