When you click the edit link to add your plans it will open a new window. Sometimes browsers will block this. Usually there is a sound and the mouse pointer will change to signal the pop-up has been blocked. The easiest way to fix this is to look for a message at the top or bottom of your browser. You should always allow Pop-ups from PlanbookEdu.
The process is different depending on the browser you are using. Here is more information for the most common ones: