You can easily add new words using found text on the Clipboard. First click the Import button on the Toolbar, then choose the Text Entry tab.
Paste the text in the large textbox, and select the options you want to use.
The “Number of words to combine on each line” option allows you to create partials from neighboring words. Enter a number greater than 2 to combine that many words into a partial.
Click Import to start and the Manual Import window will open, you can then rank words as explained here.