Open the contract for the company by going to CRM > activity > contracts and double-click on the contract.
Next, go to the 'Reminders' tab.
On the right-hand side, you can select the users/groups that require a reminder for visits and/or contract end dates, by double-clicking on them.
You can set the reminders you require and the days before the reminder pops up.
Once this has been done, the reminders will have been created and you can exit the contract.