To tweak the stats or skills your character has when you start a new game, go into the game's install directory on your PC and locate the "main.rpy" file. Open it with a text editor program like Notepad, then look for a line that says "# Initialize the statistics used by the game".
These are the starting values for your skills, listed as a pair of numbers like "10, 100." The first number is the one you want to change, edit it to any number you want so long as it does not exceed the value of the second. After you've made the desired changes, be sure to save the main.rpy file (make a backup of the original and keep it safe elsewhere just in case).
Note that your values will only take effect when you start a new game.