Open the Source in Meta Editor
Go to Tools > Options.
Navigate to the MQL5 or Compiler tab.
Select X64 Regular in the CPU architecture dropdown menu

Step-by-Step Compilation for AVX

Open MetaEditor:
Launch it from your MetaTrader 5 terminal by pressing F4.
Open the File:
Locate your indicator in the Navigator window (usually under Indicators) and double-click the .mq5 file to open it.

Change the Architecture:
Tools>Options>Comilers>MQL5> from Dropdown , Select according to your hardware
Choose X64 Regular for the widest compatibility, or AVX if your specific processor supports it but lacks AVX2.

Note: Using "X64 Regular" is the safest option as it will work on almost any 64-bit computer.
Compile: Press F7 or click the Compile button on the toolbar.
Check the Log: Look at the Errors tab at the bottom. It should say "0 errors, 0 warnings" and confirm that an .ex5 file has been created.