To those that do not know how to use. First you have to have a folder already created. Open the foldericon app and tap the icon which is in the middle to the far left on the app home page to open the lists of icons then select the one you like by a tap on it. Once selected it goes back to the app home screen with the selected icon, next to the icon is a box where you type the name of the folder you want the icon to represent. Next to that box is a copy button, tap that, now it is in the copy and paste springboard. Go to the folder you wish to change and touch and hold it until all apps and folders start wiggling. Next, tap the folder which opens it then tap the x which deletes the folder original name, then touch and hold the empty box until the word paste comes up from the springboard, then tap paste and now box should have your folder new name and icon. Hit the iPhone home button to stop the wiggling and thats it. Hope this helps someone.
To the developer:
Need new and more icons.
Johooks22 about FolderIcons