Help on creating interface between nios processro system with verilog logic

For slow signals such as leds or buttons you can just use a PIO component in the SOPC builder project, this will create input or output ports that you can control from the software.

If you need faster data transfer then you'll probably need to design a custom SOPC component. One way to do this is to format your data as an Avalon Stream and use a SGDMA to read/write the data from the main memory to/from your component. If you need to change of clock domains between the CPU and your logic, you can use a dual clock avalon stream fifo in the SOPC builder project.