Upload to the board.

I can't upload any program to my arduino Uno's board.

The following message appears:

avrdude: ser_open(): can't open device "\.\COM3": Acesso negado. (Access denied).

Someone can help me?

Do you have multiple instances of the IDE running? Or any other program that tries to use the COM port?

And sometimes windows keeps the COM port occupied even when nothing uses it anymore. Try rebooting.