Append the following sexp into whatever channel list you use.
(channel
(name 'buffersquid)
(url "https://github.com/buffersquid/guix.git")
(branch "main")
(introduction
(make-channel-introduction
"5265a73b344bc38017b80fe6a24f29eddb98c12d"
(openpgp-fingerprint
"A3DE DE93 731C B351 C891 0815 E75A 2784 63DF 3FB2"))))