Hi Kunal,

Perhaps from BIOS you can disable Intel HD 4000 graphic so that you use AMD Radeon HD 8670M , normally by default the integrated video card is disabled when there is Graphics card installed.

Firstly, you need to run 3D Mark to see which graphic card will be picked up during the test. You can use it from the below link.

http://www.futuremark.com/benchmarks/3dmark/all


Then you can update AMD driver from the link mentioned below:

• Click on the link http://dell.to/YhoaVS
• Click on ‘Download File’. Check on the radio box ‘Single-file download’. Click on ‘Continue’
• Choose the location as desktop, Click on ‘Save’, save the file on the desktop. Double click on the file; choose ‘Continue’
• Click 'OK' on ‘Select the folder’ where you want to unzip the files 
• Click ‘Yes’. Click ‘Ok’, Follow the on screen instructions and install the file. Restart the computer

In case you do not get prompts on the screen for instructions, then Browse to the folder where the files were unzipped and locate the setup file. Double click on the file; follow the onscreen instructions to complete the installation.

There are two modes in Catalyst Control Center:

• Power saving 
• High Performance 

If 'Power saving' is selected for an application, then it uses Intel graphics card.
If 'High Performance' is selected for an application, it automatically uses the AMD Radeon graphics card. You can configure it according to your preference(AMD as per your choice).

Here’s how you can configure it:

• Click on ‘Start’
• Click on ‘Programs’. Click on ‘Catalyst Control Center’
• Click on ‘Power’. Select ‘Switchable Graphics’.
• Choose an application from the list or browse and select an application and assign the appropriate GPU such as High Performance, Power Saving.
• Click on 'High Performance' or 'Power Saving' under 'Recent Applications' to change association.

I hope this helps in using your AMD Radeon graphics card instead of Intel HD while playing games. If you still face any issues, let me know and I will provide further assistance. 

Regards,
Lokesh