First steps

I created an empty SwiftUI project with UIKit App Delegate life cycle.

Then, I added GoogleSignIn and GoogleAPIClientForREST/Drive libraries to it, using CocoaPods.

To add CocoaPods to a project, run pod init in its main directory. If you don’t have pod installed on your computer, check this.

The deployment target of my app is iOS 14.0, but your Podfile must look like mine.

platform :ios, '14.0'

target 'MyVocabulary' do
  use_frameworks!
  pod 'GoogleSignIn'
  pod 'GoogleAPIClientForREST/Drive'
end

These libraries are necessary because I will need to authenticate myself to access my Google Drive files.

Finish and run pod install.

Once you’ve installed CocoaPods, close your project, open Xcode again and select your workspace. This is very important, otherwise, your project won’t build.