Framing and Sub-Flooring - Overhang supports

I have an overhang thats roughly 4' deep, and 15' long. The overhang is just the top board of the roof truss thats longer. If that makes any sense. Anyway there are 4 vertical 4x4 supports in place but right now they are simply decorative because i can easily wiggle and move them about. They are old and need replacing, how do i go about installing new supports that will actually help support the over hang. They will have to rest on concrete, which is probably why the originals are loose.

Thanks

Quite often the weight of the overhang is borne by the wall of the house, and the posts can work loose and should be fastened at the top to keep them from falling. They should not rest directly on concrete, but on galvanized post bases. Lay each post base in position and measure accurately from the top of the base to the bottom of the overhang soffit. You didn't say how they were originally attached at the top, so I am assuming a soffit board. Cut your 4x4 slightly longer and install it, fastening it at the top.