I've used Hamachi a few times before. Let's see if i can help you out.
1. Be sure your computer is connected to the internet, Hamachi is open, and your server is not running.
2. Use Hamachi to create a new group (ex: Chayes030's Private Tekkit Server)
3. OPTIONAL: for security reasons, because hamachi will leave ports on your computer as well as everyone else connected to your server's computer, i'd suggest changing the port number of the server. this is easy to do. If you would like to change the port number, follow the instructions below.
Find your tekkit server folder
Open it, and find the file "server.properties"
Open server.properties (with a basic text editor, like notepad on windows"
There will be a line that reads "server-port:" or something similar, which is currently set to the default "25565"
Change this to any number you wish. I usually use 25566, just because it's easy to remember. You can use any number. (i'd avoid using 80, 20, and 21, though, because they are web and FTP ports, which can still cause problems.)
Save the document
4. Hamachi should list an IPv4 address at the top of the program, which will be in the form of 4 octets of 3 or less numbers, ex (192.168.1.1). Copy this IP address into the "server-ip" field of the server.properties file in your tekkit server folder.
5. Start your tekkit server
6. Your friends can join your Hamachi group and connect to you by entering the IP address from step 4. If you did the steps in the code section, your friends will need to enter the IP address, followed by a ":" followed by the port number you chose. For example, if Hamachi gave me the IP address "56.72.144.58" and i used port 25566, my friends would need to enter "56.72.144.58:25566"
Feel free to DM me if you need any other help!