Magisk not fully installing


Im a complete newb at all this. please help.
GS5 not unlocked
I tryed to unlock it through Tmobile but they required me to put in a sim card from another provider to complete the unlock process… not as easy as i thought…gave up.
I completed the full root processes, installed superSU. I decided to switch over to Magisk so I uninstalled SuperSu and installed Magisk.
Magisk is showing “up to date v7.1.0”
Latest version is installed showing v18.1 but it is showing "Magisk is not installed.
Tried patch boot image file.
Please use bootbridge from adrianDC to flash Magisk… Failed
Tried direct install… Failed
Are there any step by step instructions on how to fix this?