You need to verify your domain before starting G Suite trial.
What do you need?
Login with administrator account (you received the credentials by email after registration).
Your domain DNS records access (it is necessary to add TXT record), eventually someone who may be helpful to you in this matter.
What is the procedure?
Enter your administration console via the link https://admin.google.com and login with your administrator account and password.
After you log into Admin console, approve G Suite delivery contract.
Then you are asked to change your password and to accept other terms and conditions.
Click blue button - Run the Setup Wizard.
There is a button Verify the domain. Click it.
Confirm the process by clicking Start the verifying.
Pick your domain provider from drop-down menu. If yours is not contained, pick Other.
Create DNS (Domain Name System) record according to instructions. Google will be given by evidence of your domain ownership.
Add the displayed TXT record to DNS configuration for your domain.
Click Verify option on this page.
Once Google finds this DNS record, you become the verified domain owner. (Note: Changes in DNS system may take some time. If the record is not found immediately, Google will be making regular efforts.)
If you want to keep yourself verified, do not remove DNS record, not even after successful verification.
Note: Adding this record will not affect either mail flow or any other function.
Learn more here: https://support.google.com/a/answer/60216