From top left corner got to Devices > Insert Guset Addition CD Image

Virtual CD will be mounted on /media/cdrom and you will get an autoprompt just click on run and enter your root user password.

If you don’t get that prompt just click on /media/cdrom that is mounted and you will get all the files and folders in side it just click on VBoxLinuxAdditions.run and run it as root.

Once the guest edition is installed just reboot and restart virtualbox.
Again go to Devices > Shared Clipboard and choose Bidirectional.

Again go to Devices > Drag and Drop and choose Bidirectional.

That’s it we are done. Just try to copy and paste from guest os to host os and vice-versa and it should work perfectly fine.
Same as above
Devices > Shared Folders > Shared Folder Settings.
+ symbol to add a new shared folder.Auto-mount and Make Permanent
$ sudo mkdir /media/shared-foler
$ sudo mount -t vboxsf yourfolderonhost /media/shared-folder
Here yourfolderonhost is the foldername specified on host operating system(windows/mac)
$ /etc/init.d/rc.local
$ sudo adduser yourusername vboxsf