Error occurred in deployment step 'Add Solution':
A feature with ID 15/59ad6e04-ffe4-46da-acbf-927d4eb5e3ba has already been installed in this farm. Use the force attribute to explicitly re-install the feature.
You can do it via the XML editor as well!
1. Go to your Features in your project.
2. Open the feature.template.xml file with XML Editor View
3. add AlwaysForceInstall="TRUE" to the below tag
Sharepoint 2013/ 2010