Hi Gaurav,
To answer your question. Kindly follow the below steps:
Step1: Firstly upload the "offer image" in the offer tab in Adobe Target
Step2: Create an activity, upload the "offer image" in the Experience using Visual Experience Composer (VEC).
For example. Click in any section of the VEC, where you want to see the image --> Insert Before or Insert After --> select the image option. The "offer image" will be placed
Step3: Go to Goals and Settings tab and save it. You will be receiving a QA URL. Copy and open the link
Step4: Now you will be viewing the page where you have uploaded the offer image. Inspect the image, you will be getting image URL from the developer tools.
Step5: Use that Image URL in the custom code.
If you have any queries. Please let me know