You're on the right track, but you probably skipped some steps while creating the resource
Image:
https://imgur.com/a/SgGzdExplanation:
1) Click on the name of your mod
2) Create the folders as shown in the picture: Assets -> Scripts
3) In the Scripts folder, create a new resource package with any name you want (I used "General" here)
4) Click on the package and then on the icon to add a resource. Now you should be able to accept it.
Also make sure you saved your script in your mod in the script editor (the default is in Shared)