Make sure you are trying the Cool Cursors application on the test page or any other web page except for Chrome Web Store, inner pages and Homepage. Customizatons are disabled on Chrome Web Store page by Google!
To activate Cool Cursors extension click on its icon located at Chrome toolbar. The pop-up window will appear.
Go to Cool Cursors pop-up window, choose collection you want by click on tab and choose the desired cursor and click on it.
Same way you can pick another cursor when you have played enough with the first one.
Be sure to try it anywhere except for Chrome Web Store, inner pages and Homepage.
To change the size of your cursor go to Cool Cursors pop-up window. Click "Settings" button. On the manage page use scrollbar to set the desired size.
To return the default system cursor go to Cool Cursors pop-up window and click "Return Default Cursor" button.