When your power supply has a connector that can either be 4-pin or 8-pin, it is safe to use it for either connector. If your motherboard only has a 4-pin CPU connector, check your PSU's manual to see which of the two connectors is the right one. If your motherboard has an 8-pin CPU connector, and your PSU has a 4+4-pin connector, just attach the two together and connect it to the motherboard. No worries