how to Simulate Nios II with custom component?

Now I changed my custom hardware to convolution filter that needs stream data from NIOS. But i don't know which Buffer to chose in QSYS system. I think Avalon_ST Dual Clock FIFO should work since my custom disign is much faster than the NIOS frequency.

My problem is that i couldn't find any simple code example out there that shows how to save data to fifo and how to read from.

I would appreciate if anyone give me some simple read-write-fifo code.

thanks