To sync your iOS device, you need to first open up iTunes on your computer. It’s also a good idea to make sure the computer is hooked up to a power source. Apple always asks that you have it hooked up. It will work without it, but they still suggest that it be connected.
Your computer isn’t the only thing that needs to be plugged in. Your device should be as well. It doesn’t need to be plugged into the computer, just to some type of power source, such as a portable charger.
Open the Settings App on your iOS device and scroll down to “General,” then select “iTunes Wi-Fi Sync.” This will show you all computers that are available for syncing. It also lists all the items that will be synced. You can see from the date in the picture that the last time I synced was before wireless syncing was available. This could have something to do with why my phone is running sluggishly.
If the option to “Sync Now” is greyed out on your iOS device even though the intended computer is listed as being available, you have to change the options through iTunes so that it knows that you will allow syncing to this device over wireless. Connect your device to your computer. In iTunes on the computer, select your device on the list to the left. Click on the Summary tab, and at the very bottom in the Options menu, check off “Sync with this iPhone over Wi-Fi.” At this point the device automatically starts syncing on its own since it’s connected to the computer. And because I chose this option, every time I am connected to power and under WiFi, the sync will again initiate.
This process did have some benefits. I was actually running over capacity on my phone. By syncing everything, it gave me 2.5 GB free. My phone has been running more and more sluggish. Now that I have created that free space, it might fix that sluggishness. If not, I can try restoring the phone through the backup. If it still acts sluggish, then I will know that there is some type of corrupt file on the phone, and I can than reset the phone and have it erase all the content. It’s not the desired option, obviously, but at least I’ll know it’s the only option after exhausting all others.