If one of your key goals is to grow the community, make sure your existing members know about the goal.
Let your membership know how you're incentivizing member recruitment, and consider making it a community-wide goal to reach a new member milestone. Then you can celebrate together when you reach it!
Once you’ve made the growth goal public, be clear about next steps, and provide some resources, maybe on a custom page.
One way to incentivize your members to invite their friends and colleagues is to attach gamification activity points to “invitations accepted.” This is another item you can highlight on a “grow the community” page.
If you've built it correctly, your community members will feel like owners, and will want to help achieve the goal.
When you ask them to help bring in new members, explain why. Point out how a larger, more diverse community will make their lives better, increase the resources available, or help your organization achieve its larger mission. Or maybe you just want a broader set of opinions in the community!
It's already pretty easy for your members to invite their friends; in Crowdstack, there is an "invite others" button on the home page. All they need is an email address.
You might make the ability to invite others an exclusive privilege for those who have been in the community for a while, or perhaps you want every single member to be bringing a "plus-one."