1. You login with your posting key to steemit (just like you are here now in order to leave a comment)
2. Go to https://steemit.com/~witnesses
3. Type in: intelliwitness for voting for non-top50 witness and submit
4. It will show intelliwitness and as soon as you push the upvote icon next to it, a pop up window will open saying "You must login with your active key" which is different than your posting key. So you do that
5. If you are successful, then it will be a green upvote next to intelliwitness
6. DO NOTHING. Wait 30 full seconds, then go see if you were successful on this page:
7. https://steemd.com/@intelliwitness

If you did it right, after your vote makes into the blockchain and is approved it will show you voted for that witness successfully on that steemd website page

If you don't follow this exact procedure, you will still see a green upvote when logged in via your posting key, and it makes you think you upvoted the witness. But you really didn't. It is when you actually use your ACTIVE KEY in step 4 that it actually works.

I know it is confusing...

Once you vote for a witness successfully, it says voted until you remove it.

...another way to see who has successfully voted for someone, is look at anyone's steemd.com page here:

https://steemit.com/@funnel (replace funnel with any steemit username)

On the left side margin on the bottom it will say who you are currently voting for....