Can I make press words?

I want to make this situation. First, activate notes(window). Second, I connect arduino Uno with computer. Then,,,,,,, notes is filled with a(word). Do you know any languages that can make this situation?? P.S. I am Korean. And I am not good at English. ??? ??? :blush:

I think you want to emulate a computer keyboard, and yes that is possible with an arduino uno, you will have to reprogram the atmega8(or16)u2 to use keyboard HID profile, then you can send serial commands to the 8u2 from the atmega328 nd the computer will receive them as keyboard input I don't know of where you can get the keyboard HID .hex from, so you will have to search for that you also will need to lookup how to reprogram the 8u2 with either FLIP on the computer thru the usb or with an isp programmer

Do I need to buy another Arduino??

No, but I believe it would be easier with an arduino leonardo which uses a 32u4 and ihas direct usb capbilities

If that is all you want to do, then on Windows you could achieve much the same result using a USB memory stick using the windows Autorun feature (on systems that have that enabled).