Hi Jaime. If your community is public, you can simply share the community URL with anyone on your social media or in en email campaign.
You also have the option to send Email Invitation as explained here39.
Please do not forget, to make sure the emails are not ending up in spam, you need to enable the Sendgrid app29.
To learn more about the limitation on the number of invitations you can send each day, please check out this link5.