Warning: No Clocks Defined in Design

I am building a 8 tap correlator, so the outputs of the shift registers are being used as inputs into an lpm_mult megafunction and also as inputs into the next shift register. So I just wired the output of each shift register to the input of its respective multiplier megafunction and the next shift regsiter.

I am not familiar with the reset function. What is its purpose?

I have 7 shift register megafunctions in my design (lpm_shiftreg) and they all require a clock input. I am only using clk0 in the PLL, so the output of the PLL (c0) is connected as the clock input into each shift register. I used the pin planner to assign the input pin of the PLL to the same pin on the chip that is connected to the System Clock. I have also tried assigning the input pin to CLK0 on the chip, and I still get the same compiler errors.