As a landlord you do not get the contact information for the people looking for accommodation, unless they decide to provide you with said details in a their written application or via the phone.
When your ad is published and visible for potential renters they can send you a message through our internal messaging system. You can read and answer any messaged if you go to "Messages" or https://bostadsportal.se/en/inbox/
If you however are not receiving that many applications as you were hoping for, you could consider buying an "Open ad". This makes it possible for all potential renters to contact you without paying for access to contact landlords.
You could also consider purchasing a "Top ad", this means your ad will always be displayed first in any relevant searches.
To purchase either of these options, you go to the relevant ad and activate the promotion that you want and feel is relevant.