Genymotion is almost unusable for end user like me if we cannot add or remove applications within. And Google Play Store or in this term called Google Apps is one mandatory package needed to be installed on Genymotion. With Google Apps (GApps) we can install various Android software from Google Play database.
If you already installed Genymotion, you will need this GApps for Genymotion. It supports Android 4.3. Download it now.
For older GApps for older Android version, this link should be helpful.