I don't understand how to express the stock dynamics in the stock numéraire

I have $dS_t/S_t = rdt + \sigma dW_t$ as usual under the money-market numéraire and I need to price options with payoffs

$$S_T f(S_T)$$

I don't get how to get the stock distribution with the new numéraire

Thanks a lot

I have $\frac{dS_t}{S_t} = rdt + \sigma dW_t$ as usual under the money-market numéraire and I need to price options with payoffs

$$(S_T f(S_T))^+$$

How do I express the stock dynamics using the stock as numéraire, and how do I get the stock distribution under the equivalent measure.