I will take a shower when I get home
We have two sentences: I will take a shower, and then when I get home. This last sentence is a secondary clause.
When, while, as soon as, after, before and until are conjuctions of time which introduce secondary clauses.
See how these sentences refer to future time but we use a present tense.
When my mom calls, I will tell her about my new job.
I will call you as soon as I get to New York.
While we are away, don´t forget to water the plants!