Make or edit a master server? From your previous post you seem to be trying to make a mod (I'm hoping your attempting to do something half-illegitimate).
In the case that it is a valid HL1/2 Mod, you should have no problem registering your game servers with the Valve master servers.
https://developer.valvesoftware.com/...Query_Protocol
This gives you all the technical details you will need.
If you aren't capable of registering your server, then you don't have enough knowledge to do so.
However I noticed you were previously banned, so you will probably be banned again. Anyway, have a nice day!