Physics - Find the angular frequency ? of the resulting oscillary motion.?

[syarn514]

A block of mass m = 0.630 kg is fastened to an unstrained horizontal spring whose spring constant is k = 81.0 N/m. The block is given a displacement of +0.120 m, where the + sign indicates that the displacement is along the +x axis, and then released from rest.

Find the angular frequency ? of the resulting oscillary motion.

Which formula do I use to solve this problem?