How do I access the 2nd 100 words from within the app?

While the 1st 100 most frequent words are accessible from the default activities on the front page, the entire 200 words are available from the 'Custom Activity' screen, which may be accessed through tapping on this button on the "Custom Activity' button from the main menu of the app:

Once you are on the Custom Activity screen, just tap on the words to select them for an activity:

Please note that you can scroll between pages by pressing the arrow buttons:

Note also that you can save the words you choose for later use (so that you can, for example, work on specific words given for that week, etc) by tapping the 'Save Set' button: