Hi April,
Andrian made a good point that if your Poles layer has a County attribute, you can create a filter data source using this County attribute. And depending on what context you're trying to do the filtering and/or selection, you can use the Layer Filters map tool or the Query widget as well.
If you want to do spatial selection with the out-of-the-box tools, at this point you can only use the map's current extent and not features from a data source (please see to this documentation for details). However, you can easily write an extension to do more complicated spatial operation like the one you're trying to do. I have a small sample extension that I can share with you if you're interested
Cheers,
Tif