It is natively not possible to take a screenshot on Nokia Asha 501, but there's an alternate way to capture the screen of Nokia mobile phones with the help of Nokia Screen Dumper. Just follow these steps :
1. Download Nokia Screen Dumper v3.0 and install it on your computer.
2. Then connect Asha 501 to your computer via data cable. Now a message will appear on your Asha 501 phone's screen, select Nokia/Ovi Suite from the message.
3. Make sure to exit Nokia PC Suite if it is running on your computer or else it would not work.
4. Now open Nokia Screen Dumper on your computer and click on 'Phone Connect' button.
5. Once connected, click on ScreenDump to generate a screenshot.
6. Now the captured screenshot will appear under Nokia Screen Dumper's window, simply click on 'save results' button and the screenshot will be saved on your computer's hard disk.
7. Now you can transfer the screenshot from your computer to mobile via data cable.