What do I need To write in the box for explication of changes?

[TomYoung]

You are posting to a user-to-user forum.  Nobody here can see your income tax return or your computer screen.  Accordingly, nobody has any context for your question. 

I'll make a guess that you're amending an income tax return and have come to the final stage where you're supposed to explain to the the IRS or some other taxing authority WHY you're amending.  If my guess is correct all I can say is you know why you're amending - you forgot to enter something, you got an informational return that you didn't expect to receive, (e.g., a Schedule K-1), you entered something incorrectly and need to fix that, etc., etc., etc. - so you need to write a sentence or two or three that makes it clear to the reader why you're amending.

If my guess is wrong then you're going to have to add some context to your question so someone can provide a better answer.

[SweetieJean]

Some examples:

Received corrected W-2.

Forgot to claim some medical expenses.

Corrected dependent's date of birth.

Received 1099-INT late.