Documentation help

Hello. Such a question, going through this documentation Flow Documentation
I dwell on the FCL and scripts moment.
import * as fcl from “@ onflow / fcl”

await fcl
.send ([
fcl.script pub fun main (): Int { return 5 + 4 } ,
.then (fcl.decode)
Where should I add this code, in which script? Wherever I add it, I swear at AWAIT
Also, at the AuthCluster stage, I build my application via npm run start and I have two buttons, whatever I click, I get an error “Unhandled Rejection (TypeError): Failed to construct ‘URL’: Invalid URL” can help me with this?

Do you use React? Make sure you have followed previous steps with setting up the confiugration.
If you don’t use React you may wanna take a look at the sdk flow-js-sdk/packages/sdk at master · onflow/flow-js-sdk · GitHub