I mean for most Linux derivatives, getting SSH setup for outgoing connections is usually install the openssh package from your distros repos, though I imagine many preinstall it, no reboot should be necessary, and you just type ssh user@hostname into a terminal to connect to the remote ssh server to access stuff on that computer. There shouldn’t be a need to reboot for installing app that’s not a service.
Wanting to enable ssh access to the computer you are using so a remote client can connect to it? Well the same openssh package should have come with sshd which acts as the server to allow remote ssh client to connect. It’d probably need enabling (so it’s run automatically on boot) and starting (so you don’t have to reboot to have it going), on distributions using systemd that’s usually just systemctl enable sshd.service (which makes sure the sshd daemon will be started on next boot) followed by systemctl start sshd.service to start it immediately so it’s running straight away, (or systemctl enable sshd.service --now to roll both steps into one).