How to convert contacts into leads - or - approve leads from imported outlook contacts

I have successfully imported alle my contacts from Outlook to Zoho CRM contacts (and leads). Now I understand my contacts as the "raw material" which I will approach in order to turn them into leads and then hopefully into customers (contact -> lead -> customer)

Unfortunately I don´t know how to turn a contact into a lead! Can you please help?

My second attempt involved importing all contacts into the leads section because I hoped to qualify them with the "approve leads"-function ("eads created through Web/Import will not be included in the Leads list directly. These will get added into the list once approved by the admin user."). However it seems odd that I have to browse all 5000+ contacts (only 50 per page) and can´t search for names, company and so on. Ther must be an easier way to select leads from contacts or outlook.

For example: if adding new leads, why can´t I select a contact to be imported from the contact section itno leady section?

I would appreciate your help very much, because otherwise ZoHO CRM doesn´t make much sense to me.

Best regards,
philip