If you say when something happened, Norwegian uses preteritum: i går besøkte jeg. If you leave the time open and only report that it happened, it uses har plus the participle. That is why forrige helg takes reiste, not har reist.
Examples
- Forrige helg reiste jeg til Bergen.
- Last weekend I travelled to Bergen.
- Jeg har besøkt mange museer.
- I have visited a lot of museums.
- I går traff jeg en gammel venn.
- Yesterday I met an old friend.
The mistake to avoid
A named past time blocks har: i går reiste jeg, never "i går har jeg reist".
Where this fits in
Talking about the past, Norwegian A2: Tell stories about yesterday, last weekend, and life experiences using preteritum (simple past).