Congratulations on getting your first job. This is the start of a new and interesting career.
Here are some ideas for teaching the vocabulary you mention:
e-book: you can show the students a book and ask them what it is. Write the word “book” on the board. Then write “e-book” on the board and ask students what that is. You can prompt them by asking what “e” is in “e-mail”. If they don’t know enough English, they can explain in their mother tongue.
Convert: this is not a very common word to teach at beginner level. I guess you’re teaching it for a purpose: is it in a text they are going to read? Convert is used most commonly to talk about changing money, converting computer files and converting to another religion. Take the context that is appropriate and invent a story. For example, John is on holiday. He doesn’t have much money but he has some travellers cheques. What can he do? He can convert the travellers cheques into cash. Finally, you can check understanding with the use of translation.
Function: I’m not sure which meaning of function you want to teach. The most common meanings are fairly abstract. I think the easiest and quickest thing to do here is to give a translation.