Below is what I understand on how DNS and FTP are used...

My question is, how do they interact with TCP/IP?

DNS and FTP are protocols which are the part of the ISO 7-layer protocol stack. FTP is an application layer protocol while DNS is a layer 4 protocol, thus it falls under the transport layer protocol. Every packet that these protocols use have to traverse all ISO layers and thus they also pass through the TCP/IP protocol, FTP in particular, as that uses TCP as the transport layer whereas DNS uses UDP as the transport layer. DNS and FTP deal with Windows too. They are basically two of the major network protocols used. DNS is basically the name given to all the name servers on the Internet. This is how we find a particular website amongst millions on the Internet. It's like having an address for each site and the requests send by the client are sent from a DNS server to another until they reach the destination. FTP is a way of transferring files or receiving files from a remote/local server. Many people use this protocol to upload their websites to a web server. It can also be used to retrieve logs and syslog files from a syslog server. It's uses are extremely vast.