How to Solve or Fix virtualbox ata2 master and slave unknown device

ata1 master: VBOX CD-ROM ATAPI-6 CD-ROM/DVD-ROM
ata2 master: Unknown device
ata2 slave: Unknown device
ata3 master: Unknown device
ata3 slave: Unknown device
Or virtualbox ata2 master unknown device
ERROR :- 


SOLUTION
Step1 :- Click on setting after that click on storage then click on new IDE "+" button right side of top see image

Step2 : - click on choose new virtual optical drive to add

Step3 :-Search where you have download the boot2docker iso image
Example :- C:\Users\cloudnetwork\.docker\machine\machines\default


Step4 :- click on ok

Step5 :-Click on start button

Output :- See below screenshot of image of both finally output came

And