I dont think anyone has answered the question correctly.So, for anyone else who has the same question, this should help :
Step 1 Go to Build>Generate Signed APK>Next (module selected would be your module , most often called “app”)
Step 2 Click on create new
Step 3 Basically, fill in the form with the required details. The confusing bit it is where it asks for a Key Store Path. Click on the icon on the right with the 3 dots (“…”), which will open up a navigator window asking you to navigate and select a .jks file.Navigate to a folder where you want your keystore file saved and then at the File Name box at the bottom of that window, simply enter a name of your liking and the OK button will be clickable now.
What is happening is that the window isnt really asking you chose a .jks file but rather it wants you to give it the location and name that you want it to have.
Step 4 Click on Next and then select Release and Voila ! you are done.