Hi how can i set imessage profile pic

Go to:

Settings > Messages > Show Contact Photos = "On"

The pictures in your contacts should then appear in your messages. To add a picture for a person, Go to Contacts. Then select the person's name and tap "Edit" in the upper right corner. Then tap "add photo" in the upper left corner.

You can assign photos to contacts in the contacts app itself or in the photos app. Take a look at this.

https://www.imore.com/how-assign-photos-contacts-your-iphone-or-ipad