How to execute VHDL and NIOS II block in the same design

Hi,

I'm a newer in FPGA design, and i need to use 2 block (NIOS II and VHDL) to program a sequence on a DDS AD9914(Is a direct digital synthetizer).

I don't know how to do.

When i simulate the bock one by one its work like i want, simulate together (i mean connected to the same i/o of FPGA) there is nothing that work

I whant to execute first the NIOS II and then give the hand to the VHDL block.

It's anyone can hel me??

Best regards