How to install a skin in Minecraft Bedrock
Installation depends on the format: PNG skins use the character editor, while .mcpack skin packs import automatically.
Check the format
An individual skin should be a correctly sized PNG. Skin packs normally use the .mcpack extension.
Add a PNG skin
Open Dressing Room or the character editor, choose a classic skin and import the PNG.
Import a skin pack
Open the .mcpack file with Minecraft, then find the new pack under Classic Skins.
Keep the original file
Avoid resaving the PNG in messengers or image editors because they may change its size or transparency.