The wall charger is of no use at all. It isn't possible to use a circuit designed for 100 - 240 V input and run it from 6V.
As I understand it, you want to charge a cell phone from 6 V when it was designed to run from 5V.
The first suggestion that springs to mind it just to connect it up. If you are getting 6V no load from the hand generator, what will probably happen is that the cell phone will take quite a bit of current and the 6V will drop to much nearer to 5V, and a cell phone designed to accept 5V will probably not be damaged by 6 V anyhow.
If you don't want to be that brave, you want a low-dropout 5V linear regulator.
Low-dropout means that it will work with a small voltage difference between input and output, like you have. Regulators that are not low-dropout can drop anywhere up to 2.5 V so you wouldn't get more than about 3.5 V with a 6V input.
A linear regulator is the simple type that gives out slightly less current than you put in. The alternative, call switching regulators, are needed when you increase the voltage or make it negative, and are more efficient if the input voltage is much bigger than the output. None of those apply here, so you should keep it simple.
Something like
https://www.electro-tech-online.com/custompdfs/2008/03/KA78R05C.pdf is very easy to use. All you need is big capacitors to ground on both the input and ouput. The bigger the better, and not less than 100 :mu:F