Revisited this and answer is that on my system the little box to be ticked to activate the Velvet add-ons is way over the opposite end on the left hand side, next to the little triangle that opens the add-on data.

On revisit I noticed the part that says
“These images may differ slightly from what you see depending on what version you have . . . ”
So that meant that things might be ok but a bit different so felt confident to do a second deeper probe to get on top of this.

So, the answer is:
There’s a small grey box there that you can click on to activate the add-on on the lhs next to the little triangle
Looks like this:

> SMALL GREY BOX : : velver_revolver : :

Once that was done, the box that wasn’t there before to setup a link to the FFMPG program’s ffmpg.exe file was now there. All sweet after that

Using Windows 10 and Blender 2.77

The warning Bang Bang asterisk thing?
Just the Blender developer/maintenance crew messing with us : )

Can I just congratulate you all working on this for my first ever easy-to-understand and not leaving me in a desert-of-bewilderment intro to an open source program.

It’s been a while since I did this, and that total turn-off is completely absent due to the efficient and effective results you have come up with in this process.

Professional, user-friendly, clear and effective.
Thanks so much.
I have donated and will again.

regards
Lorraine