To assign stats, click the icon next to each score to cycle through the different stats. Each stat can only be assigned to one score, so stats must be cycled back to the blank gray icon before being assigned to a different score. To re-roll scores, press the die icon in the bottom-left. Alternatively, press the green flag in the top-right (this will also reset stat assignments).
Use this tool to generate ability scores for your D&D character, then choose which scores go to which stats to optimize your build! Thanks to Gary Gygax for making D&D, obviously. The sound effects used are from Fire Emblem 7: The Blazing Blade. Phosphorus link: https://phosphorus.github.io/#230535735 (faster)