How to Network/ Lateral for a 2021 SA Position at BB

Hey, I was hoping I could get some tips/ advice on how to network efficiently, in order to land a job within my same firm next year. I'm a rising junior in Argentina (I'm a US citizen), currently an intern for the Latin America Credit Risk division at a top tier BB, and I'm looking to join the LatAm M&A group at my current bank next summer, as a SA. My internship here in Arg. ends in November, but the applications for the SA Job open in July. Here are a few questions I had: Should I try networking with people using my job email? Or my personal email? Would it be too unprofessional to just message them through the internal chat system? Should I be contacting people from the Latam group in NY, or should I first try to network with people in IB here in arg? Also, Should I try to contact people from HR (internally)?

Any insight would be appreciated! Thanks.