Use the Simple Past:

for actions that happened and finished in the past

for actions that happened in the past and we know exactly when

with time expressions such as yesterday, then, ago, last night/week, in 2001...

Use the Present Perfect:

for actions which started in the past and continue up to now

for actions that happened in the past but we don't know the exact time

with time expressions such as for, since, ever, never, yet, already, so far, how long...