2nd externship location, even if you plan on using same location as 1st, requires it's own approval. This is because of the different requirements for it. Here is a link concerning the paper work for externships. At the very bottom is a link containing preliminary information. I also saw some where you cannot start the process until all courses are completed and passed.
Externship Paperwork Guide
Externship 2 Update 2016 - FAQ
Veterinary Technician Clinical Externship Information