i have #include <Keyboard.h> in the sketch but it just keeps saying the same thing when i wanna compile it to the arduino uno
Keyboard.h library is not suited for Arduino Uno
This question appears on the forum every week.
but it says on their website that its compatible for the arduno uno
No, you need a board with native USB support for this - for example Arduino Leonardo
is there another alternative for the arduno uno
Arduino Uno doesn't have a USB support, you have to choose another board
If your Uno has a 16U2 TTL-to-USB converter, there are ways around it. Some google searching: arduino uno as hid - Google Search. If you board is a clone with e.g. a CH340, it will not work.
But another board (Leonardo if you want to stick to the same form factor) is preferred.