How do you connect a nad c270 amp to the bose 901 series vi equlizer and system/

Bear in mind that 901's require exclusive use of any amplifier they use. You shouldn't expect to use conventional speakers alongside them on the same amp. The reason is that the 901's require the use of their dedicated Active Equalizer to shape the frequency spectrun to match their drivers' response curves, resulting in a flat sound output. Applying that kind of equalization to any conventional speakers will sound to sharp at the extremes and may even potentially damage them.

For connection I would run a pair of RCA cables from the L&R Audio Line OUT of whatever preamp or source you're using to the Active EQ's Line IN; then the EQ's Line OUT to a NAD amp's Line IN. DEselect any Tape options on the Active EQ, attach the 901's to the new amp, set the NAD volume controls pretty high (and leave them alone), run through any level setup procedures in your control electronics for volume, etc and you're done.