Stuck on escaping (after chamber 19) Screenshots included

[toattett]

Hi, I am on my way to escape from Aperture Science Lab??
and I got stuck...
I enter this "room" and I see the text "Over here" written on the wall with an arrow pointing upward?
I opened a portal and got up top? Then I see the red text written on the wall for exit? But I can't get over because there are wire fence block the way? Some help please!! Thanks!

 

[Pesmerga]

The floor of the upper level looks like a nice place to put a portal.

 

[toattett]

It worked! Thanks!