Let’s say you want to copy or move files from a Windows drive into your WSL instance. You could use /mnt/c/path/to/file from within WSL, e.g.:
cd $HOME
mv /mnt/c/Users/youruser/Documents/project/myproject .
Another way is to access the WSL instance’s drive from the outside.
- Navigate to 
\\wsl$\Ubuntu-20.04\home\your_usernameand drop the files there 
Please note that WSL prohibits access to any root-owned files or directories through the \\wsl$\<distro> share.
- Create a directory under root 
/andchownto your user:sudo mkdir /project sudo chown $USER:$USER /projectYou should be able to drop into that folder as well.