This tense is not as frequent as some of the others you have been studying but it denotes an action in the future which is prior to another action in the future. e.g.
Nous vous téléphonerons quand nous serons arrivés = We'll call you when we get there
1st action in the future = nous serons arrivés
2nd action in the future = nous vous téléphonerons
The 1st action uses the futur antérieur because it will happen before the 2nd action which is also in the future.
The problem I think is that in English after expressions of time like 'when', 'as soon as' etc.. the present tense is used. But this is not the case in French.
Take a look at the following lesson with lots of examples if things are still unclear -
Hope this helps!
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