1. Make sure you are running Jelly Bean 4.2.2 Build 15.3.A.0.26. Go to Settings > About to verify this.
2. Enable USB Debugging , Go to Settings > About phone and tap 7 times on Build number to enable Developer options, now Go to Settings > Developer options to enable Enable USB debugging mode.
3. Enable Unknown Sources. Go to Settings > Security and check Unknown sources.
4. Download vRoot from here - http://www.mgyun.com/vroot
Yeah it is in Chinese, so bear with it :P , download it and install this software just click next next like u install any other software :P
5. Open the vRoot and Connect your phone Xperia L to your PC , you will see a green Root icon in vRoot, click on that to start the rooting process. See the below screenshot.
6. When it is finished your phone will restart automatically and vRoot will show something like the below screenshot.
7. Congratulations your phone is now rooted :P. To verify see the Kinguser app , see the note below to replace it with SuperSU.
Note :- If you want to change the Kinguser (Chinese Superuser app) to SuperSU , just download SuperSU from Playstore , open it , it will ask for Root Permissions , grant it , then follow the screen instructions to update the binary. Now open SuperSU , go to Settings and click on "Install SuperSU into /system" . Your phone will reboot and Kinguser will automatically get uninstalled
Download this file - LINK
Extract it somewhere and run 'runme_win.bat' .
Chinese for the VRoot