BlueStacks works similar to any android device hence in order to use it you need to complete the sign in process.
When you try to access app store you will be prompted to sign in first. For this you need to complete the "one time setup" process as shown below, click on the continue button at the bottom of this page and then select the sign in option
Our one time set up allows to use already existing id only. Add your credentials and continue with the onscreen guidance.
You will prompted to select the account account you wish to add. Select the account and click on "ok"
Click on continue to enable app sync
You will be prompted to put in your password again and sign in. once you sign in you can see the three step registration process to be complete.
If you face any difficulty/error to complete the one time set up process you can try the steps in the URL below
If you still face any issue write to us at firstname.lastname@example.org