As soon as is a conjunction. You use as soon as to say that something will happen immediately after something else has happened.
Be Careful!
You usually use the present simple after as soon as. Don't use a future form. Don't say, for example, 'I will call you as soon as I will get home'. You say 'I will call you as soon as I get home'.
When you are talking about the past, you use the past simple or the past perfect after as soon as.