Easy! first of all, I am guessing you are using StarterPlayer since you referred to your character as a model. In order for everything to line up perfectly and have every character spawn like this as soon as they join the game you will not have to use StarterPlayer. In order to solve your problem, you will have to look in the "HOME" tab in studio then head towards the right hand side of the tab where it says "Game Settings" with a literal gear icon above it, press this. Once you have pressed it, you will be greeted with a little window. From here, click the "Avatar" tab on the far left. Moving forward you will be able to insert ID's for anything that is customizable on the roblox avatar along with choosing if your game will be strictly R6, R15, or player choice. Hoped this helped! Any more questions please let me know and if this didn't work or if I didn't write something clear enough, please write me back and I will be happy to fix it for you!