In order to edit your advertisement, you have to be logged in to Bookafishingcabin.com.
First, make sure you are in the Owner Profile (select 'Owner profile' in the top right corner of the website).
In the menu, click on 'My fishing cabins' to get an overview of your advertisements.
Click on the button 'Edit fishing cabin' of the listing that you want to edit.
Don't forget to 'save' when you are done editing.