Need Scroll Bar in Pop-up Window

On our website for our workshops, we have a “Click here for more information” pop-up window. It does not fit on a smaller laptop screen, so I would love to add a scroll bar for those who need it.

I know it is something easy, but I have not been able to find anything.

Suggestions fervently welcomed! An example may be found at the bottom of our Portugal page at

Many thanks, I hope,

Barefoot Contessa Photo Adventures

this may depend on the browser. I opened it in Firefox and Chrome on my 13" laptop and a scroll bar along the bottom was already there.
For vertical scrolling, the scroll bar on the Portugal page will allow for scrolling up and down.

Thanks, Rod. Some glitch in my Chrome hid it, but when I rebooted the browser, all was/is well. Perspicacity of inanimate objects and gremlins at work.