Customs icons not displayed

I am trying to use custom icons and I copied the zip file to locus/icons/ folder as mentioned in the manual but the icons are not used/displayed. In settings --> navigation --> advanced settings --> navigation cursors the selected source is now "default" and when I click on "Customs icons" I am redirected to the url describing how to use custom icons: https://docs.locusmap.eu/doku.php?id=manual:advanced:customization:icons&s[]=custom&s[]=icons

On this page is mention: choose which icons (internal Locus or any of your files) you want to show in the icons selecting dialog but I have no clue where I should do that. I believe I followed the instructions correctly but I might have missed something. Thanks in advance for your help.