Firebase is fundamentally a collection of tools developers can rely on, creating applications and expanding them based on demand.
Create a Firebase App
First, you should create a free Firebase account and create a new project there. You can visit firebase.google.com and signup if you don't have an account with Google earlier, and if you have an account, you can create a firebase app project. You can enter the project Name and Select Region, and it will create a Firebase project for you.
Once the project gets Created, Navigate into Overview menu on the left side there you can see project overview and under that click on project settings and Add Firebase to your android app as displayed in the below screenshot.
After that, it navigates to the page where you can enter your android package. To get the package name go to android >main >Android Mainfest.XML there you will find package name then click on register app, and you will find an option to download the google-services.json file as displayed in the below screenshot
Once you download that you need to copy that contents present in the downloaded file then navigate to your project file directory inside that src>android >app >google service.json file open that and paste the contents you copied earlier.Then move to your project directory there you can find fire-store service .dart folder inside that you have to replace the following
googleAppID: you can find it from google service.json file
gcmSenderID: go to firebase.google.com there when you sign in in left corner there is project overview >cloud messaging under that we can find senderID
apiKey: you can replace client ID from google service.json file
projectID: you can find this from google service.json file from project folder
and navigate to fire base .google.com click on next and run your application to verify installation and click on console .