In order to import your Warehouse Location from your Magento account into Appath, you will need to first check out this forum post, that explains how to export Custom Attributes from Magento.
Next, you will need to simply enter the Warehouse Location attribute exactly how it is in Magento, to your Magento Setup page in Appath. Therefore, if ‘Pick Location’ is how this attribute comes up on your Magento admin page, this is exactly how you need to enter it via Appath as well.
Also, please note that there are two types of attributes in Magento: ‘system’ and ‘user-defined’. Please make sure to set your attributes as ‘user-defined’ so that they can properly be exported to your Appath account.