From the author's README on Thunderstore

Lil Peep GBC Whitetee.

Front — GBC- Back — nothing

Install

Extract the Lil_Peep_GBC_Whitetee folder into your ReSkate mods folder:

<ReSkate>\Mods\Lil_Peep_GBC_Whitetee\

The default location is:

C:\Games\Skate\Mods\

Launch ReSkate and the mod is picked up automatically. To equip it, open the character's clothing and select the tee on the top slot.

If it does not show up, open the Mods tab in ReSkate Studio and make sure Lil_Peep_GBC_Whitetee is ticked in the load order.

Uninstall

Delete the Lil_Peep_GBC_Whitetee folder from Mods\ and relaunch.

Install Lil Peep GBC Whitetee

You need ReSkate and your own copy of skate. on Steam.

Open ReSkateLauncher.exe and go to MODS.
Search for Lil Peep GBC Whitetee and click install. The launcher also installs anything it depends on.
Press PLAY. In game, the MODS tab of the ReSkate menu (Insert) turns it on and off.

Or install it by hand: download the .zip and drop it on the launcher window, or unzip it into its own folder in Mods\ beside Skate.exe.

Maps show up in the ReSkate menu's level list. To join a server running a custom map, you need the same map installed. If the game won't load after installing, see known issues.

skatemods doesn't host or review this mod. The download comes straight from Thunderstore. Only install mods you trust, because scripts can run code.