LAN party creation explained based on my deep experience and knowledge.
DO NOT use Internet TCP/IP! Instead Use Local (LAN) TCP/IP as demonstrated in the image below.
One of you creates a lobby while the others join.
If the joiners can not see the lobby name e.g. (Alex's Game). All of you should temporarily turn off Windows Firewall, as well as Enabling UPNP in the router and disabling upnp of all your machine using this utility https://www.grc.com/unpnp/unpnp.htm
(Make sure the status of upnp tool is green)
SOLUTION 2: Using AoE2Tools and Voobly
This solution will also set you up for multiplayer and playing other people online (over 4000 players).
Download the latest version of AoE2Tools from here https://github.com/gregstein/AoE2Tools/releases
Install and press scan then the tool should be able to detect your cd installation then make the game completely playable on Voobly without any further configuration.
You can either Press "2 - Start" button in AoE2Tools then press Fix Voobly Not Found (Which installs voobly automatically), or you can go to Voobly.com and download the client manually.
Sign up an new account for all users from here https://www.voobly.com/signup (No need to add real emails because the accounts don't need verification).
Now Login in each computer with the username not email.
Once successfully logged into Voobly; a game browser window should pop up then you can join either "New player Lobby" or "RM/DM Medieval Siege". (can't see game browser? File > Game Browser from the messenger menu)
Now one of you creates a room, change its title name while the others join the same lobby and find the room with that title name.
Once all players are in the room, the host can press launch and the game will start for all of you (nobody clicks resume lobby button).
You will notice that the game start in window mode but that's fine once all of you are ingame it should go full screen but if it doesn't you can Press F10 > Options > then select your preferred resolution.
Another the advantage of setting up AoE2Tools and Voobly is that anyone of you or all of you together can play multiplayer against other people.