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First you need to create a Gmail/Google account if you have not already have one. You can create a new Google account from here --> https://accounts.google.com/signup?hl=en
Then you need to make sure you have connected your S7 to WiFi network. To do that, open Settings app from the list of apps on your phone. Tap WiFi. It will show the list of WiFi networks in there. Select your WiFi network and enter your password ***** asked. This will connect it to WiFi network.
Now to the part of downloading apps, you need to open Play Store app in your phone. Play Store is the name of the application store of Google. Open Play Store and you will find the apps in there. You can download the apps from there by selecting them and clicking Install button. If it asked for Gmail/Google account, enter the one you already have or created earlier.
This will allow you to download applications to your phone.
If you have any difficulty on following the steps above, please let me know and I will continue to help you