Here's what you need to patch your Mac using the OpenCore Legacy Patcher

• A Mac with OS X 10.9 Mavericks or higher
• An appropriate OS X/macOS installer app (download here if you need one)
• A USB stick with at least 16GB size
• An OpenCore app (download here)

After you made sure your device fits all the requirements and you have all the resources you need, let's proceed to the OS detection method.

How far can I go with OpenCore Legacy Patcher?

Technically, OCLP can patch any Mac with Intel to any OS, but practically, OCLP is usable only to patch your Mac to the OS X/macOS version, which is the successor of the next macOS version after yours.

Let break it down using a following example: the Mid 2012 MacBook Pro's newest compatible macOS release is macOS Catalina 10.15.7. With OCLP, your Mac can be patched to macOS 11.7.2 and it'll be still usable. OCLP can also upgrade you to macOS 12 Monterey, but it's not sure if your Mac will be as easy to use as before - although the 15-inch Mid 2012 MacBook Pro was lagging after upgrading to macOS 12, the 13-inch Mid 2012 MacBook Pro is working flawlessly.

After some prep for surgery, let's start the patching itself!

Patching

First of all, you need to make sure that you have a backup of all of your files on your Mac. We strongly advice you doing this just for safety case. The Time Machine backup is in any case also good.

Now it's time for the procedure:

Step 1: make a bootable installer for your OS (read more here)

Step 2: after you made the bootable installer, open the OpenCore legacy patcher

Step 3: Now, on the screen that has just appeared, ...

... click Build and Install OpenCore.

Step 4: After your OpenCore configuration has been built, you'll get a prompt. Click Install to disk.

Step 5: After the process has been finished, quit the OCLP app and restart your Mac while holding the Alt key. Make sure that your USB is in the USB port.

Step 6: When you see the available boot disk destinations, select EFI boot with the navigation keys (◀︎ to go left, ▶︎ to go right and ⏎ Enter to select the boot destination). In the new menu that has just appeared (you should see OpenCore text on the border of your screen), select the "Install macOS {version name}" bootable installer that you've made a while ago (◀︎ to go left, ▶︎ to go right and ⏎ Enter to select the boot destination).

Step 7: After 3-7 minutes, you should see a menu with 4 options. Select the second option (It should be called "Install macOS {version name}"). Go through all the steps, select the drive you need and start the installation!

Now, you'll get the casual OS installation as you typically see when you are upgrading to the new macOS version.

After several restarts, you'll see the login screen - simply type in your user password, go through a minimised version of a Setup Assistant, and you are done!

Now, you can take out the USB stick!