You can start using Google+ by creating a personal profile.
Creating a Google+ profile
1. Sign in to your G Suite account.
2. Click the portal icon in the up right corner.
3. Select the You+ icon.
4. Fill in at least the following details: Name, Gender, Birthday. Click Upgrade.
Note: The given birthday isn't needed for anything else except to confirm that you are over 13 years old and thus eligible to use Google services.
5. In the next screen you can add friends to your Google+ circles. This can also be done later. Click Continue.
6. In the next screen you can start following things you are interested in on Google+. This can be skipped/done later. Click Continue.
7. On the final screen you can add personal details and a photo to your profile. These are all optional. Click Finish when you are done. Your profile is completed.
Note: If you want to hide your profile from Google+ search (so that people outside your organization can't easily find you), go see the instructions here.