To open these accounts in bulk you can use office365 admin panel import pane. But without going to admin panel you can manage this tedious work using powershell.
The following powershell script will help you to
- Create Accounts
- Assign Office365 License Pack you have
- Export Created Account details including assigned temproary passwords in NewAccountResults.csv file.
Beforehand you should have list of your staffs details in users.csv file.
Then you should send the temproary passwords created to the personal email acounts of your staff by using the following powershell script.