how to use the USB transfer data to FPGA

I also don't know which do you mean.

the USB connector maybe represent USB-Blaster.

you can not use it as data-bus.

but just sending throw the data ( not communicating all the time).

you can use it as JTAG.

one simple example is just write a code in NiosII.

such as ...

//-----------------------------------------------------------------

unsigned char myData[] = {0x00, 0xff, 0x22 .........

.....

......

//-----------------------------------------------------------------

download the code via JTAG.

your memory has whole data when NiosII program starts.

if you want to store the data.

why don't you store data in the Flash memory.

any questions?