Download link: http://commonerrors.blogspot.com/2014/11/download-juniper-router-iosimage-for.html

Step-1
Open the download image with VirtualBox

Step-2
open GNS3 and creat VM with these VMs

Step-2
Set number of interfaces and start simulations.

"if you are having any issue with gns3 router console then you can use VM console for configurations"