Add a new instagram widget

Follow the instructions here.

Categories Widget

If you want to display all the categories (labels) from your blog, leave the widget as it is.

If you want to display specific categories (labels), do this:
1. Go to Layout > open the "Categories" widget.
2. Click on "Selected Labels" > "Edit" > select the categories you want to display > click on "Done".
3. Save the widget.