If you have recently started out in teaching, I suggest you get a good course book and base your lessons around that. You will be able to use the units of the course book to present the language, to practise it and use the exercises you have found as extra practise. Ask the school you are working with if they will also buy the teacher’s book for you; the teacher’s book should be a good resource and should guide you through the teaching. They might already have books available.
On the whole at beginner level, aim to teach concrete vocabulary (i.e. things that can be seen or touched) before moving onto the abstract. In 15 hours with a beginner student, you will cover only the very basics in grammar - present tense of “to be”, present simple questions, negatives and affirmatives including use of have got – I don’t think there will be time for very much more. You should also aim to teach a good amount of basic vocabulary.
Beginners need a lot of practice and repitition; you should practise language in a variety of ways in order to maintain the student’s interest. You can use the course book and the exercises you have found for practise.
I don’t agree with teaching question tags in the first fifteen hours with a complete beginner. If the student is not a complete beginner you might be able to do some work on question tags; only start this after the student has mastered the tense involved.
You could also look at the link below.
Please feel free to write in again if you would like more specific ideas or if the school cannot provide you with a course book.