When an adverb modifies an adjective or another adverb it appears immediately in front of the word it modifies.
Modify an adjective - He saw a very beautiful lady.
Modify another adverb - She quite slowly turned to see us.

You have a choice when it modifies a verb. You can place it before the verb or after the verb.
Or it may appear at the beginning of the sentence.
Adverb before - He softly spoke to the children.
Adverb after - He spoke softly to the children.
Adverb at the beginning of the sentence - Softly he spoke to the children.

The functions of an adverb.
Adverbs typically add information about how, when, where or to what degree.
How - slowly, quickly, willingly          When - rarely, frequently, tomorrow
Where - here, there, everywhere       To what degree - very, quite, more

Adverbs take different forms.
How adverbs especially are formed from adjectives by adding an ending of "ly." slowly, quickly, willingly
Many common adverbs do not end in "ly." apart, away, aloud, now, not, out, in, once, often, only, then, soon, sooner, too
Not all words that end in -ly are adverbs friendly, neighborly, anomaly, mealy, scaly