As of writing, the custom-global type package only provides IE 11-compatible definitions of Map/Set/WeakMap. Adding definitions to this type package should be a last resort; in general, changing the lib option in tsconfig.json is a better approach (the IE 11-compatible types aren't available as a lib option).

The custom-global types are not referenced by default in most projects. To add a reference, add the following to tsconfig.json compilerOptions:

"typeRoots": ["../../node_modules/@types", "../../typings"],
"types": ["custom-global"] // and any other types you reference