How to import Tasks and Events?

Scenario 1: Tasks/Events related to other CRM records:

Currently you cannot import tasks and events related to other CRM records from the Activities module. However, you can import these records from Setup > Data Administration > Migrate from other CRM page, provided they have the proper mapping-relationship with Leads/Contacts (Related ID) and other CRM entities (What ID). You can use this option if you are importing data from other CRM systems.

Scenario 2: Independent Tasks/Events:

You can use the Zoho CRM - Outlook Plug-in to synchronize your tasks and events between Outlook and Zoho CRM. For more details, refer Synchronizing Outlook Calendar with Zoho CRM

Related Links
How do I import Notes, Tasks or Events and associate it to other records?
How do I set up reminders for my tasks and events?