Log into your 123-reg e-commerce package.
Click Content/Categories and select New from the drop down bar.
Choose Image gallery from the list shown, give the image gallery a name and then select yes to make the image gallery visible on your site.
Click Insert to add your image gallery.
To administer your image gallery:
Simply click Content/Categories and select Datasheet view from the drop down bar.
Now click on the image gallery you wish to administer.
Click on the Images tab
You can now add or delete an image.
Also within this section under the General tab you will be able to change the size of your image and the layout of your gallery.