The very first thing you have to do is answer Mr Sánchez's e-mail so that we know you have received the information. If you didn't get the confirmation form or the letter, please let us know and we will send it again.
Then, you should write an e-mail or letter to your host family (in English, of course) introducing yourselves and saying whether you are allergic to any food or there is something you really can't stand. The e-mail/letter doesn't have to be long. I'm sure you won't have any problem with it. Here is a list of the things you can include: name, age, likes, hobbies and interests (I like, I love, I enjoy . . . ), dislikes (I don't like . . . )
If you have any questions you can e-mail me (firstname.lastname@example.org) or write comments here.