Steps to create scatter file for your current ROM:
Step 1: Unrar the downloaded file using 7-Zip and open MTKdroidTool
Step 2: Connect your phone to PC via USB cable. If MTKdroidTools doesn’t detect your phone then in your phone go to Settings -> Developer Options and select USB debugging. If there is no Developer Options in Settings then go to About phone and tap Build number 7 times to enable Developer Options.
Step 3: Click Blocks Map button in MTK Droid Tools
Step 4: Click Create scatter file button
Step 5: Select the location where you want to save scatter file and click Save