Re:amaze Push Campaigns will send to any user who has allowed your site to send notifications to their device. When a visitor to your website accepts push notifications permissions, this will increase your audience count. If you already have a mechanism to request this from customers, then Re:amaze will automatically add visitors to your site that have accepted push notifications to your audience. As a member of your audience, they will receive any Push Campaign sent via your Re:amaze account.
If you do not yet request push permissions from your website visitors, you can build a Re:amaze Cue to do so! Go to Settings > Cues to build a new Cue and add a button to "Prompt for Push Permissions". When users interact with that Cue's button, your site will request permission to send notifications to their device. Once that is done, they will be added as an active subscriber to your account, and future Push Campaigns will be sent to this user!
Below is a screenshot of how simple it is to create this Cue: