Hey Madelyne, "as" in Spanish may be translated in three different ways depending on the way it is used in English.
As in "while this is happening".
As the temperature rises, water becomes vapor.
A medida que la temperatura sube, el agua se convierte en vapor.
As you speak there are three other persons waiting.
Mientras tú hablas hay tres personas más esperando.
As in "like".
She speaks as a native speaker.
Ella habala como un hablante nativo.
Say it as you said it before.
Dilo como lo dijiste antes.
And finally, as in "since".
As she did not know how to get there, we had to call her mother.
Como ella no sabía cómo llegar, tuvimos que llamar a su madre.
Ya que ella no sabía como llegar, tuvimos que llamar a su madre.
(Ya que or como can be used indistinctively here).
As you have already made a decision, go on with your plans.
Como ya has tomado una decisión, sigue adelante con tus planes.
Ya que has tomado una decisión, sigue adelante con tus planes.
(In this case, the "ya" in the first sentences is not related to the "ya que", "ya" wihtout "que" right next to it, means "already", as in "she is already here", "ella ya está aquí. In the second sentence the "already" of the original sentence in English has to be left out to avoid the kakophony (a bad sound) of the double "ya", but it is understood).
I hope this helps you.