adverbs are most frequently placed right after the conjugated verb, as in:
J'ai bien dormi. -- I slept well.
Il doit vraiment faire ses devoirs! -- He really must do his homework!
But exceptions exist. Here is a good site that explains where to place them: http://www.frenchlanguageguide.com/grammar/placement.asp
Or here, another good one: https://www.lawlessfrench.com/grammar/adverbs/
Greetings, -- Chris (not a native speaker).