As you see the error from above screenshot, it mentioned that yum command is locked by another application. Meaning that someone already run the yum command and the process is running.
To find out which process and user holding the yum lock, just enter following command:-
From the above screenshot, PID 11290 is currently run by root user and holding the yum lock.
It is very easy to solve this issue, first wait the process finished. Second is kill the process ID. Below is the command to kill the PID
kill -9 11290
Now you should able to use yum command.