if your psu has an 8pin cpu line, use it, if not, find the fourpin one and carefully fit it into the cpu socket, should be the lowermost four but its formfit so you 'cant' get it wrong,
modern cpu's need mre power so they changed it to 8pin, if you struggle with bsod's on 4pins, one solution maybe to get a better psu and use the 8pin on that
As stated above, use 8-pin if you have it. Reason it reduces the I sq R drop accross the pins - more eff.
As to requirement. 8 pin was incorporated for the "OLD" pentium D extreme Edition and for MBs that provided for Daul processors. 8 Pin is recommend for Processors drawing 125 Watts or greater. Not required for Procs with a 90 Watt rating, But as I stated does provide a benifit.