Make sure that you have activated Subscriptions in Settings:
When you activated Subscriptions, you can see Add new subscription option in Estatik plugin sections.
Click on Add new subscription and fill in the form that is opened.
Check below explanatory screenshot to fill in the fields correctly:
1. Property qty - Quantity of listings that this specific Plan allows to add.
2. Featured qty - The number of listings that can be marked with Featured label.
3. Period - The period of time after which this specific Subscription plan will expire and needed to be prolonged to be valid.
4. Currency - Currency for Subcriptions prices.
5. Price renewal - Sum of money that must be paid to renew Subscription plan.
6. Trial period - In case if Admin will decide to offer free trials, this is the field where you can select periods: Week, Month, Year.