To use a Digipeater with Winlink Express, simply choose the "Digipeater" option when selecting a station in the packet radio session. Then, enter the dipeater callsign and SSID (the nubers as the end) in the box showing "via." One example is connecting to N9JN-10 via W5ETX-3. In other words, your signal will "hop" from your station to the W5ETX-3 and then hop again to N9JN-10.If you imaging your are on one side of a creek and the Winlink node is on the other, then it's kind of like hopping on a rock to get across a river. You can hop on several digipeaters, but remember, each hop takes time and the more you add, the slower your connection will be.
Some digipeaters have mailboxes attached to them (think 1980s computer BBS systems). You can leave messages and check for mail to you. They are not connected to the internet, so the messages will not forward to another system.