Unless you're a scientist or researcher in a field that would be performing research at McMurdo, your best bet is probably to apply for a support position with one of the organizations or parner institutions listed here: https://www.usap.gov/jobsandopportunities/

Though as the blog mentions in an earlier post[0], you may have to re-apply repeatedly over the course of several years.

[0]: https://brr.fyi/posts/basics

I kept hoping I could trick NASA into sending me down there for a few weeks. Surely a senior Linux/Unix admin would be useful there? Ah, well, there's always the tourist option.