You may want to import the slider after the dummy data has been imported. The sliders in the Wish theme demo are packaged with the complete theme zip you download. Extract the zip you downloaded, find the sliders folder and you will find slider zips. The complete theme zip should look like this after you have extracted it:
You will find the sliders zips inside that folder, it should look like this:
Now you need to navigate to the Revolution Slider page in the wordpress dashboard:
Now hover over the slider box and click Import Slider:
A popup box will show up and you can import any slider from the Browse button and click Import Slider:
You can repeat this for all sliders if you want to import all of them.