Making a hard object to a smooth object

How do I make a hard object, for example a square, into a smooth object like a circle? I got a object I am making and I have a spot that needs to be smoothed off and round and it is square.

SirMikey

In edit mode select the vertices then press ‘W’ and click Subdivide Smooth. The more you set the percent up the more it will be smoothed. Also remember to click SetSmooth for the mesh.

Another technique could be to use Subsurfacing on the object.

Ahhh ok thanks