How do you stretch Five Ten Project climbing shoes?

The 5.10 Project climbing shoes are not stretchable, they are not designed for that. The place where your toe knuckles rest is the only place that can be modified or change shape but that occurs during the time you are still breaking your shoes in where your shoes is adapting with with yor feet. The 5.10 is an agressive bouldering or sport shoe which is made to stay in its original shape in order to execute more complex and advanced moves.

If the shoes are easily stretched, its ability of providing control and sensitivity to the climber which is needed for agressive and overhung routes/problems decreases.

Since this pair is agressive, there is a high chance that the shoes will hurt when you use them which is a price that you have to pay to gain more control. Most people who use these kind of shoes only use them for two to three climbs before relaxing their feet for a bit.

If you feel like the pair that you have is too small, then exchange them for a larger pair but make sure that they are not too big because then, you will lose some of that control that the shoes offers right from the start.