Coventry Carol

I came home from choir practice, last night, with sheet music for the 2 carols we have to sing in our parts. The leader asked who could read music. Only a couple put their hands up but then she didn't tell us HOW to read music.

She asked the organist to play each of the four tunes for us to sing to in turn. 
So, is that lower set of notes on the stave with the treble clef with the A alongside it what I should be singing as an alto?
Do I start on a D?
How do I know what a "D" sounds like if I don't have a piano?

My daughter told me to record my line on the phone if she plays all our parts for us again next week.

This is going to be hard. The mens' tenor voices on the pew behind me are so strong, I'll want to copy them. The Homegroup ladies who were with me say we'll have to practice when we meet on Wednesday mornings! They're all sopranos.

I choose the music for the things we sing on Wednesday mornings but I think the rest of Homegroup will get sick of The Coventry Carol and Unto Us Is Born A Son every week for the next 5 weeks.

My attention was distracted from singing this afternoon as 2 of us got together to contact the speakers for next year's Social Club. Our next speaker on this year's calendar is a blipper!