July 2017 security update starts rolling out to T-Mobile's Samsung Galaxy Note 5
Before you proceed with the downloading and installing of the update, you need to check your battery to see if it is charged to at least 50%. In addition, your phablet needs to have a data connection, preferably one to a Wi-Fi network. T-Mobile also reminds you that while in the middle of updating your device, do not touch any buttons, remove the battery, or turn the phablet off. Interrupting an update in the middle of installing it could result in permanent damage to your Galaxy Note 5.
Keep in mind that while the security update is being is being downloaded, you will not be able to make or take any calls on your device. That includes 911 emergency calls. Because the update is being disseminated OTA, it might take a few days before it hits your phone. You can try to manually have the update arrive on your Galaxy Note 5 by going to Settings > Tap Software updates > Download update manually. The phone will then automatically check for an update. If one is there, click on install to start the updating process.