Accessing the source file with a virtualbox installation

Hello, How can I get access to the source file with a virtualbox installation, I tried to connect with filezila but the access but denied. I noted my ip by doing ifconfig or else ip addr, then typing identifier and typing password. Can you give me the best solutions. thanks in advance

The solution I found:
1 / Ubuntu installation on virtualbox: INSTALLER UBUNTU SUR UNE MACHINE VIRTUEL (VIRTUALBOX) - YouTube
2 / Erpnext installation How to Easy Install ERPNext V13 on Ubuntu 20.04 || frappe || Erpnext || Tamil || Linux || Ubuntu - YouTube
Attention when ordering: $ sudo python3 --verbose --production --user username - key-branch version-13 --erpnext-branch version-13, I got an error, so I retyped this same command a second time and it worked, so this command do it in 2 times