You should really use a knife straightening tool (which is a pair of offset hardened pins set in a sturdy handle) so that you can apply the bending force precisely. If you don't, you can end up with a wavy blade instead of a bent one....
I straightened my cheap stainless steel yanagiba using a vice slightly opened, sadly after I tired to grind it flat on the back, so now the concavity is messed up and the edge isn't as good as I'd like. Worked pretty well in that the knife is now straight, but poorly ground (as it was anyway) and it's rather ugly. Cuts OK though.
If you don't have something like a large vise, you need to trap the blade between a heavy object and a table where you want the correction to occur and bend the rest of the blade from the handle end to get the bend out. You may have a single "kink", or a gradual bend, I cannot tell from the picture, but in either case you must determine where the back deviates from flat and apply correction. A single bend is fairly easy, just go slowly and don't try to get it straight in one try, you will likely over do it and have a bend the other way. Multiple bends, or a curve, is harder to get rid of. Mine had one major bend and two small ones closer to the handle.
With some practice you will be able to tell when you have reached the elastic limit of the blade and feel it "give" with more pressure. First time or two you reach that point you will probably go too far, which is why I recommend gradual stages.
If you do have a vise, leave the blade loose between the jaws, don't clamp it. The bends are rarely sharp, you need to spread the correction out over the same length as the bend, which you can adjust by how far apart the jaws are. If you are worried about scratches, you will need to pad the corners of the jaws. I didn't bother as my knife cost me less than $25 so I don't care, but a better one I'd want to keep looking very nice.
Peter