Reading Data in PC from MAX10 FPGA board

Communication between PC and FPGA can be done via UART - just use the rs232 uart module in qsys. You will need to connect it to an avalon master like nios. Then you can write data to the uart module which will spit it out at your desired baud rate on 2 pins (UART RX and TX). You can buy a simple UART to USB converter for under $5 to interface to the USB port on the PC.

What exactly are you doing with DSP builder? If you have some values you want to connect to avalon memory map from DSP builder you can use RegFields (look it up the the DSPBA manual). This will let you write values to specified address location in the memory map. You can then use NIOS to read those values and write them to UART.