Head over to Appearance > Widgets, and look for the sidebar widget.
It looks like the widget link should be http://www.mwsservices.org/gallery, but that page gives a 404. What link do you want the button to link to?
There is no sidebar widget in the widget section.
Go the Appearance > Widgets, and find the sidebar widget.
Then look at the bottom of the bottom widget for some code that will look something like this:
<a href="http://www.mwsservices.org/www.mwsservices.org/gallery"><img src="some url.jpg"></a>
Replace http://www.mwsservices.org/www.mwsservices.org/gallery with http://www.mwsservices.org/shop/
What widget areas do you see on the right side of the widgets page?
There is available widgets section on the left with some widgets listed below it but on the right there is a primary widget section and a secondary widget section with nothing listed underneath.
Try clicking on the arrow beside the primary widget section or secondary widget section to drop down widgets.
I did and nothing drops down.
Could it be that I dont have access to that widget? There is one other person who updates our website as well and maybe they do.