The vast majority of showers are built with the same type of single handle control...they work, but they all have some sort of max temp stop built into them to pass code. They are set at the factory for 'normal' water temperature, which may not be normal for many people. It is quite common to have to readjust that limit once it's actually installed, and it should be part of the installation procedure you paid for.
Even the thermostatically controlled valves may need calibration, but they're usually able to compensate. On them, they may have an indication of what the temperature should be (in degrees), and you calibrate it until that is correct, if necessary. After that, it will automatically hold that temperature by adjusting how much cold is fed in. A conventional single-handle valve starts out at all cold, and as you rotate, decreases the amount of cold while increasing the amount of hot. The safety stop prevents you from (in most cases) getting to all hot to prevent scalding. In the winter, with cold incoming water, you may need more hot to be comfortable.
It's a very simple thing, once you identify the type of method they use on your valve. If you don't have the installation instructions (the plumber should have left them with you), on a new valve, you should be able to download them from the manufacturer's website. Personally, I'd tweak it now if you're wanting to use the shower. I see no big reason to wait as long as you don't go overboard and adjust it so it can be scalding...I'd go a little past your comfort level, but still tolerable. It will be hotter in the summer with the warmer cold supply, so you don't want to go overboard, but still be able to make it comfortable after a cold snap when the cold water can plunge in temperature, too.
