Yes, you can manage DNS for your domain through My Pages.

I want to manage DNS for my domain externally

In this case:

1. Contact your external DNS service provider to obtain name servers for your domain.
2. After obtaining name servers, edit domain's name servers to match the ones you got from the service provider.
3. Contact your external DNS service provider for further details how to modify DNS records.

I want to manage DNS for my domain at Svenska Domäner

In this case:

1. Go to domain's main page and verify that your domain is connected to the service.
2. If the domain is not connected to the service, please connect domain with service.
3. If the domain is connected with the service, verify that there is no DNS configuration issue.
4. Click on Control Panel in order to access and modify DNS records of your domain.