There is nothing to say, just example..

cat /etc/systemd/system/ssh-scocks-proxy.service
[Unit]
Description=Socks proxy via SSH
ConditionPathExists=|/usr/bin
After=network.target

[Service]
ExecStart=/usr/bin/ssh -NTC -o ServerAliveInterval=30 -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -i -D user@remote-server.com

# Restart every >2 seconds to avoid StartLimitInterval failure
RestartSec=5
Restart=always

[Install]
WantedBy=multi-user.target

(c) https://gist.github.com/drmalex07/c0f9304deea566842490
(c) https://blog.kylemanna.com/linux/ssh-reverse-tunnel-on-linux-with-systemd/