Import Bulk Devices to Fortigate 81E

Hi everyone, 

I have a FortiGate 81E, and I need to import some company devices and then, create a devices group and an IPv4 policy to control de wifi network access. 

I can import devices by using the CLI, but, can I use another method? A GUI method?

The second question is, have I an limit number of devices to import? 

Thank a lot for your help.