Let me try to guide:
- Go to pakwheels.com/login (preferably via laptop / desktop, and not on smartphone)
- Enter your particulars
- After successful login, you will see your name on the upper right corner
- Move the mouse cursor there, a drop-down menu will appear
- Click on the first one, i.e. profile
- "My profile" will appear
- In the first row, there will be a button "Choose file" (it will upload the pic / dp, which ever you will choose)
- Browse & Select the pic and let it upload
- Click on the "Save Changes" button at the bottom of the page
- Let the page refresh / reload
- Hurrah, your dp has been changed!
I hope, it all helps. Thank you. 
(Please let me know and share, when you are successful after following above steps. You can change your name, and many other things there too, in the profile section)