Just present yourself, in the best way, but honestly. Be prepared with some of your own questions about the theatre, if you don't know about it. Or even doublecheck things you think you know, so it shows that you're interested in learning about them. "So, I see that you have a proscenium theatre...and you do NOT have a fly space, correct?" Have in mind what you'd like to learn from the job, as well as what you've done in the past that can best help THEM. And be a real person, not some overly sweet trying-all-the-right-answers person. You do already have one person who spoke well of you, so you're off on the right foot.
I'd recommend having either pen and paper or a computer in front of you too, during the interview, so you can take your own notes...you'll probably be so nervous you'll forget much of what was discussed...you can refer to it later, or even back during the same interview.
And there will always be more interviews...we hope.
Best of luck,
Erin