You can follow the below steps:
1) Login to your EMM panel
2) Click on Admin->Account Configuration
3) Click on Edit against Image Hostin Domain.
4) Enter the image hosting sub-domain in the text box. Please note the A record for the sub-domain should point to 202.162.244.9, i.e. the A record for img.yourdomainname should point to 202.162.244.9
Example: Point the A record for the img.netcore.co.in to 202.162.244.9
5) Click on Save