1) Go to 'My fishing cabins', select the listing you want to edit and click on 'Edit fishing cabin
2) Click on 'Rates' in the horizontal menu
3) Click on 'edit', on the right-hand side of either the 'Base rate' or any 'Special Rate' you want to edit.
4) The 7th line from the top shows the option 'Extra guest pricing' to charge a surcharge for additional guests. You determine above how many guests you want to charge extra.