To include TypoScript from an external file you can add this line to the setup or constants part of a template record in Typo3 Backend:
<INCLUDE_TYPOSCRIPT: source="FILE: fileadmin/typoscript.ts">
To see your changes immediately, you should add the no_cache flag to your default config:
config.no_cache = 1
This disables the caching of your TypoScript.