How to mark a pin and/or net as being a clock?

I have an input pin in my design that I am using to bring in an external clock signal. I created a very simple test case where my entire design consists of a single DFF, which I clock with the external signal I'm bringing in.

I am getting the following warning:

"Warning: Node: ext_clk_sig was determined to be a clock but was found without an associated clock assignment."

I tried marking the input pin as a clock in the assignment editor by adding an "assignment name" of "global signal" set to a value of "global clock". This assignment has its "enabled" field set to "yes".

Apparently I need to do more to get the Quartus compiler to treat my clock signal as a clock. Timing is critical on this signal. What do I need to do to make it clear to quartus that this pin needs to be treated like a clock?

I really hope I do not have to use one of the dedicated clock pins. I do not have access to these on my current hardware platform.

LH