First you must go to bulk process page by clicking Bulk -> Import button on top right corner of page. Then you click New Request -> By Upload Excel.
After that, you must follow step for uploading by first downloading excel template, and fill data on the excel with your own.
This is sample data for importing contact, please make sure all cell format was "Text". Then submit the data, but those data will still need confirmation to be imported (please see next step).
Your request will be processed, make sure to keep eye on those requests. If status of those requests are Waiting Action then you can import them into contact (or you can choose whats contact need to imported or not) on request summary.