HodlBot has a very simple referral system. If you share HodlBot with a friend and they pay for a HodlBot account, you'll get 1 month free.
Sharing Your Referral Link
You can find your referral link in the settings page.
Sharing Your Portfolio
You can also share your portfolio by clicking on the share icon of any portfolio on your portfolios page.
If someone pays for HodlBot after viewing your portfolio, they'll also be counted as a referred user.