No, SNMP is a very old protocol where the correspondingly activated service on your host offers information of its status to outside requesting servers (like your Icinga server) if these were added to an access list.
The whole point of SNMP is that it needs less set-up on your client host than other methods. On both Linux and Windows (Server) it is already present, but needs to be enabled. For vn. 3 of the protocol, in addition to that access list, you need to choose the mode, and then decide on i.d. stuff within that mode, e.g. login and pass phrase; this has to be set up on every host. (Under Windows you can use global policies to set it up once for many hosts. Probably something similar is possible for non-Windows op. systems, but I haven’t had much experience there…)
Then you need to find SNMP-able plugins in the WWW to download for your specific requirements - usage meters, interface monitors, health checkers, whatever. Some manufacturers of specialised h/w offer an SNMP-able Nagios-type check, or something more specific; you may have to check your install kit for that h/w, or contact the manufacturer.
Some scripts out there are pretty good, some not so well built (the latter may e.g. request too much info over time, e.g. by doing a request for every liitle bit of info, rather than doing a “bulk” fetch for all they need at once)…
Of course, all the requesting plugins for all the hosts run on the Icinga server itself, therefore not balancing the load more toward the hosts. But for most small to mid-range computer centres, SNMP is a valid alternative that your Icinga server can handle, as a rule.
P.S. (late edit): I just realised you may only want the configurative steps for SSH… Sorry, but there are quite a few good instructions findable in the WWW for that - look for descriptions of the generic “check_by_ssh” plugin; here’s a good German one: Icinga check by ssh Plugin – Thomas-Krenn-Wiki.