1st, you need to check the location where you have installed genymotion.
2nd, Supposing it to be default downloads folder. You can enter this folder by typing these commands in the terminal:
$ sudo su
then you will be prompted for root password, then type
$ cd Downloads
here in the Downloads folder you can see the list of files typing ls
If you see genymotion
directory then enter the directory typing cd genymotion
then type ./genymotion
and it will run the application.
You are good to go now.
In case your default installation directory is something else then enter that directory and follow the last 2 commands(cd genymotion
and then ./genymotion
)
Let me know if there is any problem.
sudo chmod a+x ./genymotion
. That will do it.