How To Remove This?!

how to remove the who is online at the bottom of my forum?

To remove it you need to go to your Administration Panel and click on the Display tab. Once clicked on, navigate to Structure and hierarchy. Here you will find an option which reads "Display viewonline information box on index :" Set it to "Never", and then save your changes.

admin panel>display>Structure and hierarchy>*scroll down a little*>"Display viewonline information box on index=never">then hit save

Hope this helps.