If you have downloaded the complete theme package from themeforest.net, you need to extract that zip first. Then you will find these files:
You will find the demo data xml file (dummy_data.xml) inside the Demo Data folder.
If you have just downloaded the installable theme zip, you can download the dummy data Here (right click > save link as)
To import the dummy data for Wish theme manually, you need to go to wordpress dashboard as an admin and click import page under Tools:
Then you can let it install WordPress importer plugin and activate it:
Now you can import the dummy data file from inside the Wish theme zip you downloaded in the dummy data folder and click Upload and Import:
This should take only a few seconds and you will get all the dummy pages and posts.
Dont forget to create and add menu items from Menus page under Appearance.