Trying to access FTP behind a firewall

Hi, I'm using WinScp library SessionOptions with the following code:

SessionOptions sessionOptions = new SessionOptions
{
Protocol = Protocol.Sftp,
HostName = txtUrlAConectar.Text,
UserName = txtusuario.Text,
Password = txtpasswordftp.Text,
SshHostKeyFingerprint = txtkeydeseguridad.Text
};

I'm opening session with its options, but how can I set the outgoing firewall values?
I mean, I'm behind a firewall trying to get out and then finally reach the sftp server.
Is there any option in SessionOptions to set firewall username and password? I've already have an open port at that firewall, opened by the Firewall Administrator. I'm just needing to specify those three parameters: username, password and port, when I attempt connection.

Thank you!

Please read documentation:
https://winscp.net/eng/docs/rawsettings

If that does not help, come back.