You can invite your friends just by starting a chat with them on LOOK. Your friends don't need the app to chat with you. You can start a chat with anyone in your Contacts and they can participate normally over SMS until they download the app.
You can also tell your friends to search "Look" in the App Store or Google Play Store and download there. LOOK supports iOS and Android!
To see people nearby and quick add friends, open the Search tab to see who is nearby to you.
To send an invite link to a friend: Groups tab > Me page (top right icon) > ❤️ Tell a Friend > Select Friend to invite