There are two main ways to confirm your CC is BGC. You can either disable all packs when loading your game or you can check in the package warehouse tab.

Pickypikachu - How to make stuff BGC with S4S

Using S4 Studio to confirm your item is BGC

Sims Community - How to Disable Packs

The Sims 4 How To Disable Packs - James Turner

Use this tool to automatically create a command with the required packs disabled.

If your item is not BGC, use the below tutorial to make it BGC. Note: Recolors are commonly not made BGC as no alterations are made to the mesh itself.