Settings > Shared Folders > Add New Shared Folder
Folder path: <insert_here_hosts_path>
Folder name: <name_of_the_share_on_guest>

Select “Make Permanent”.
Leave unselected “Read-only” and “Auto-mount”.

Make sure the virtual box guest tools are properly installed in the guest machine.

After that, edit /etc/fstab and add the following:

Downloads /home/myuser/Downloads	vboxsf	rw,exec,uid=1000,gid=1000,dmode=0755,fmode=0644 0 0

This is an example for a shared called “Downloads”.
This share will be mounted under /home/user/Downloads forcing uid/gid to 1000, which it will be the one related to the myuser