We use Present Perfect tense to talk about action which started in the past and continues up to the present. For and since are used with the present perfect to indicate time.
We use for to talk about a period of time (a few days, half an hour, two years...)
- He has studied in Dublin for 3 years.
- We have worked for 2 hours.
We use since to talk about a specific point in time, or a time when the action started (last year, June 8, 9 o'clock...)
- We have learnt Spanish here since 2002.
- I have loved you since the first time I met you.