Click on the 3 dots icon in the right-hand corner of the Sites Widget, then click on Edit Parameters

A Sites button will appear. Use it to open a dropdown list of all available sites. Scroll through the list and select the site you want to associate with your widget

Click on this 3 dots icon, and you can sort which types of sites are shown in the list, either solar, wind, or both. By default, both types of sites will be shown, if available