adverbs usually end in -ly (quickly) and describe a verb.

The thief quickly jumped over the fence.
(How did he jump over the fence?) Quickly.

It's difficult without an example, but an adverb generally tells when or how pertaining to the verb, or it can further define an adjective or even another advervb. For example... I came home very late. Both very and late are adverbs.

It you look for any verbs in the sentence that it could modify. If the adverb was "quickly" ask yourself what did he do quickly?
So for example, The boy quickly jumped off the horse.
What did he quickly do? He quickly jumped.

hope that helps!