The condition won't appear on the map view of the process. It should be contained within the activity to which the conditional process is attached.  eg Task 4b Perform credit check if customer is new. (Condition process attached 'Perform credit check')

Because the conditional process is a process in its own right, it will have its own set of triggers and inputs etc.

Thanks Noala.  I guess that does the job.

And then, is the assumption that the process flow returns after executing the optional process?

In which case, if I want to show a situation where the current process doesn't continue, I need to use a decision box?

With a conditional process it will usually have a two headed arrow line indicating that after doing the conditional process then the flow returns to this process and continues on.

I recall seeing either a help article or Youtube that explained how to change the arrow heads on a condition link ages ago but don't seem to have it saved sorry.

From memory you do this via the Inputs and Outputs sections   ie if the conditional link is in the inputs it will only have an incoming arrow head and if it's in the outputs it will only have an outgoing arrow head.  Sorry I don't have better info than that, have a play and I'm sure you'll work it out (if this functionality still exists).