On this page of the Forza Horizon 5 guide, you can read how to change your character's appearance and what are the available personalization options.
You start Forza Horizon 5 by creating your character. Your character appears mainly in the cut-scenes and on the podium when you manage to get a top position in a given race.
It is worth remembering that you can also change the appearance of your character later in the game. To do this, you first need to get your first home, which you will unlock over time by completing a few initial races.
Once you own a house, go to it and then select the tab where you will be able to change your character's appearance. In addition to the appearance itself, you can also change the gender, voice, victory emotes, and even how you want the NPCs to address you (He/She/They). Unlocked items will always be at the very beginning of the list, while those locked will be highlighted in gray, with the option of purchasing them for a certain amount of credits (CR).