I transferred the files from my local computer to the remote directory using WinSCP, but I'm curious if I can restart/reboot the server using the same application or i need to do that using PuTTY.
I don’t think you can. WinSCP is a SFTP client, SFTP its a subsystem of SSH, but that does not mean that you can achieve everything you can do with SSH.
Here’s a complete list of commands supported by the SFTP protocol -> https://www.ssh.com/ssh/sftp/#sec-SFTP-Protocol
As you can see there’s no such ‘reboot’ instruction nor anything similar.
EDIT
As other answer says, WinSCP has the ability to issue remote commands https://winscp.net/eng/docs/remote_command
So you can do Commands > Open Terminal
and issue a reboot