Here's a little introduction to Command Tasks: [LINK
Basically it works like this:
You specify the command to be executed in the "Command" field, then enter any arguments for that specific command in the "Arguments" field and optionally enter a "Working Directory" (this is the path where the executable is looked for but can be left empty for all commands that are in the PATH environment variable).
So your ping example should look like this:
Working Directory: empty
Now the real fun comes in the form of Replacement Tokens which can be used to inject values from a context connection into the command task. You can, for example use the $URI$ replacement token to inject the URL of the selected connection into your ping task. All available replacement tokens can be accessed from the little buttons with the arrow icon on the right of all command task text fields.
One last tip: Royal TSX ships with two command tasks by default, Ping and Trace Route. They are stored in the Application document under Tasks. To try them out, simply right click one of your connections and select "Favorite Command Tasks" - "Ping" or "Trace Route".