In Roblox Studio, I am trying to when I spawn, I will look different then my original roblox avatar.
Use this plugin: https://www.roblox.com/library/752585459/Load-Character
OR Right Click on the model and click Accessory. If this answers your question, then please accept my answer.
If you want to make a custom character or change your oeiginal charatcter use HumanoidProperties, you can change anything you want like the character size, aniamtion, skin color, ect,.. Hope this helped you out and have a good day!