I have 2 Sharepoint lists in SP2013: Errors and Locations. The errors list has a lookup column to the locations list. I need the location information (phone, address, etc) to populate automatically into the errors list via my the location number that is already in the errors list when I paste in my errors (from Excel). How can I do that? Right now, I have to open each item, edit it, and select the location from the lookup dropdown.
SharePoint lists with connections like that have to be set manually (though you may be able to find a way of doing this via code, I wouldn't recommend it) The same is true for calculated fields, they only update when the field is updated.
On the other hand you can go to your List tab and (depending on the version of SharePoint, the list settings and your permissions) switch to Datasheet View, which will allow you to update in bulk as if working with a spreadsheet.
This image is from SharePoint 2010