OK, I got it to work.
For the sake of those who may ask the same question this is what I did:
1. I added the library "TabStripViewPager" library by checking the checkbox in the Libraries Manager.
(I am not sure if "TabStripViewPager" was in the library list before as I did not notice. If not, I cannot say for sure how it got there)
2. Then I went to the Designer and added the TabStrip. (Add View > CustomView > TabStrip)
3. I then added the Dim to the code from within the Designer. (Right-click TabStrip1 > Generate > "Dim TabStrip1 as TabStrip")
4. Then I added the line: #AdditionalJar: com.android.support:support-v4
to the code.
It's working now.