Hi, I bought a new Iphone 6s and made a backup of my old Iphone 5. The backup is visible in my new phone but it's not clickable. Help anyone?

Are you trying to access the backup during the initial setup or have you already setup the new phone? If you have already done the initial setup, see the instructions below from Transfer content from an iPhone, iPad, or iPod touch to a new device - Apple Support

To transfer a backup to a device you've already set up, you need to erase the device: Tap Settings > General > Reset > Erase All Content and Settings. This will erase any data that's currently on your device. After you've erased it, your device will restart and you'll see the "Hello" screen. Now you can transfer a backup to your device.