By invitation. Howard sends you a one-line command; it adds this computer to his private network so he can help manage it. You stay in a waiting room with no access until Howard approves you.
Use the exact command Howard sent you - it includes a key in front (TS_AUTHKEY=...). The examples below show the shape; paste Howard's real one.
macOS / Linux
TS_AUTHKEY=tskey-… curl -fsSL https://join.howardkessa.top/join.sh | sh