Don't Manually Install If You Feel Uncomfortable
The Galaxy J Android Pie update is rolling out slowly and it'll take awhile to complete. If you don't want to wait for your Android update you can manually install the software right now if you have the correct device and some free time.
The official Galaxy J firmware is out which means you can skip the OTA (Over-the-Air) roll out and manually install the software yourself.
If you're feeling impatient, you might be tempted to go this route, but you should only go through with it if you feel comfortable with the installation process.
If you feel uncomfortable with any part of the manual installation process you should hang back and wait for Samsung/your carrier to push the upgrade.
Manually installing software can cause major issues (it's possible to brick your phone) so if you aren't feeling one hundred percent confident, skip it.