Upgrade Procedure Through FMC for Firepower Devices
Procedure
Step 1. Navigate to System > updates and look for the version you want to upgrade to, as shown in the image.

If the version that you want to upgrade is not shown on the screen, continue with step 2.
If the version that you want to upgrade is shown on the screen, continue with step 4.
Step 2. Upload the upgrade files on the FMC. Navigate to system>updates and click on Upload Update, as shown in the image.

Step 3. Choose the file that you want to upload and then select Upload, as shown in the image.

Step 4. Select the install icon, as shown in the image.

Caution: After the upgrade the system perfom a reboot
Step 5. Choose the device and select the Install button to start the upgrade, as shown in the image.

Step 6. Verify the upgrade process on Notification Icon > Tasks, as shown in the image.

Verify
Firepower Management Center Upgrade
Navigate to Help > About to verify you have the desire version, as shown in the image.

Firepower Devices Upgrade
Navigate to Devices > Device Management andverify you have the desire version, as shown in the image.

Troubleshoot
If the upgrade procedure fails, generate the troubleshoot files and open a TAC case. Please refer this guide in order to generate the troubleshoot files.