Reactor provides a lot of functionality but sometimes you need to do custom code. This is accomplished by adding a custom.css or custom.js file to the assets zip.
Visit your App in the admin and click the build tab. Scroll down to assets and add a .zip of files you want to include locally in your app.
Adding Your Custom Code
Do not put your files in a folder before zipping them. Select the files and compress them on their own.
PLEASE NOTE! (Custom code is outside Reactor support, you are on your own!)