You have several options of how to invite players to your team.
You can use the "Invite to the team" button in the player's profile which can be accessed by clicking on player’s name in leaderboards or invitation window.
Also, you can invite a player from the list of suggestions on your team's page.
Another option is to push the "Invite more" button on your team's page and invite suggested players or friends.
Or send a link that is shown at the bottom of the same window.