First is the easiest.

After installation, when you rightclick a folder you find 'Mark Folder' in your rightclickmenu and it has a submenu.
In the subemenu you find the default folders in a variety of colours and on the bottom there is the option 'More icons'. Like this:

When you click 'more icons' you get this:

And then choose the tab 'User's icons'.

There you can use the "add" button to browse to your own files and add those and then you can use them in two easy steps.
Two - because you always need to go to 'more icons' before you can choose your icon.

But we want more don't we?

Ok, so you have a icl file of your choice that contains exactly the same amount of icons as the colors.icl does that comes with FolderMarker (36 icons that is).

Now you browse to the location where FolderMarker is installed. (Probably C:\Program Files\FolderMarker)
Make a backup copy of the entire folder on another drive, just in case ;)

Inside the folder you find a subfolder called 'icl' which contains icl files (hey, we didn't expect that did we? LOL). One is colors.icl
Replace that with the one you have made or downloaded. Do NOT leave the old version inside the folder with another name or so.

If FolderMarker doens't show your icons the way it is supposed to, this is also the location where you can delete faulty files, so FolderMarker will rebuild a new cache.
But ... when you do that all references to icons located in there will be lost. So folders you have changed the icon for will be reset to the default icon.
Therefor it is better to replace the icl file(s) located there, when you need to.

When done also run Disc Cleanup and set it to clean 'thumbnails' (in Dutch 'Miniatuurweergaven').

If that's not enough for it to catch on, you can also restart.

But then you should have what you want!

If you look closely you can see your folders have a slightly different preview now:

And this time when you choose Dark > Red you get this:

Now that looks a lot better doesn't it???

sara, this is very good. thanks...

But I'm not done yet ;)

When you get it from GAOTD it is fully registered.
However when you go to 'More Icons' and the tab 'Everyday' you'll see a red textline saying this is not the full version blabla. That is just saying it is not the biggest form of icl file they supply.
They want you to buy more of their icons. (Logically)
But you can delete that icl file (Everyday.icl) or replace it with another and the tab disappears and with it voila the text is gone ;)
Keep in mind when you replace Main.icl or Colors.icl you have to use an icl with the same amount or more icons in it, otherwise the program get's very confused ;)
If you have no use for ABC you can delete that icl and the tab will disappear.
(Don't forget to clear it from the cache too then!)
In the same way you can add as many icl files as you like.
They will show up as added tabs.

Never delete or rename Main.icl or Colors.icl though! That will make the app crash. It needs those files for it's appearance in the rightclickmenu.

LOL - I see now you already posted in between!

Thanks guys;)