Preparing the boot image file

•Ensure that you have put the magisk app, Odin tool, and Stock Firmware file in the same folder since you will need them frequently during the procedure.
•Enter into stock firmware folder and extract the “AP” file through the unzipper.

•Now tap on a newly extracted folder. There, you have to right-click the boot file.
•Choice 7-zip then select the “Add to archive” option to change archive format.
•Select and change the archive format from .lz4 to .tar, then hit the OK button.
•Copy the boot.img.tar into your Android smartphone for the patching process.
Patching the boot image file
•GET and install Magisk App and tap 
 the install option inside the app.

•Now tap on a newly extracted folder. There, you have to right-click the boot file.
•Choice 7-zip then select the “Add to archive” option to change archive format.
•Select and change the archive format from .lz4 to .tar, then hit the OK button.
•Copy the boot.img.tar into your Android smartphone for the patching process.

Patching the boot image file

•GET and install Magisk App and tap on the install option inside the app.

•Navigate to the storage unit part where you have saved in device boot.img.tar.
•Once you tap on that file, the patching process will automatically be initialized.

•From this, you will obtain the magisk_patched.tar file at the exact location.

•Deliver that .tar file to the PC, and connect your phone into GET mode.
•Turn off the phone, and press both volume keys while connecting to the PC.
Flash the patched boot image file
•Open the Odin Flash Tool, there, you will notice that the device is connected, but if that’s not showing in your case, perform the last two steps once again.
•Head toward the “AP” section, then drag and drop the magisk patched .tar file.

•In the left corner, you have to untick the “Auto-reboot” option to boot manually.

•Now, simply tap on the start button to initialize the final patching procedure.
Re-installing the Magisk App
•Remove the data cable once the flashing process ends, then press and hold the Volume down + Power Button until the Samsung logo with alert appears.
•Release both buttons and long-press Volume Up key to enter in the recovery.
•Apply the factory reset setting and safely reboot your phone in the usual way.
•GET the Magisk App from this article and install it properly, so it works.
Once the reboot process end, the magisk will fully install with your phone, now enjoy!

Post credit @crankyV2