Port check means: SMON sends tcp request to certain port if port is not available then alert will raise.
If you want to use only the "port check" left empty other options
HTTP status check means: SMON sends http/https request to certain port, address and URI if answer is not 200 then alert will raise. The "URI" means: address after Domain name, for instance: "/" or "/index.html" or "/info".
If you want to use only the "HTTP status check" left empty Body option
HTTP status also includes port checking
BODY answer check means: SMON sends http/https request to certain port, address and URI if answer do not consits properly phrase that was set for searching in the body answer then alert will raise.
BODY answer check also includes HTTP status and port checking
How to start using RPM you can read here
For SMON updating you should run next command, if a new version is available yum will offer update it:
|Login (without "@"):|
|RPM or/and Docker?|