Click on Management > Carrier:
Each Carrier can be both client and vendor. To use a Carrier as a client, you just need to create ingress trunk. To use a Carrier as a vendor, you just need to create egress trunk.
Once you see the Carrier listing, you can click Create:
In the "Create New" page, you can fill out the Carrier detail. The basic fields you need are : Company Name and Contact Email.
After submit, you will be asked to creat ingress or egress trunk.
For vendor, you will click "Egress Trunk".
You just fill out the vendor trunk detail. Then, your vendor is successfully created.
Within the Egress trunk you created on Step 2, you can see the list of tags on top. The tag that let you to create tech-prefix is the "Action" tag:
You can see the following after you click into the Action tag: