Hii I've switched from Windows 10 to Linux Mint. In Windows 10 I used to have WLM (CrossTalk) but on Linux I'm not sure how I'm supposed to make it work
I did receive advice from someone but I lost the source I received
I was wondering if anyone knew how I could do this? I know there's a way but I'm a huge newbie with Linux and I'm not that great with PCs in the first place haha... 
There aren't many WLM apps for Linux. So your best bet is either to use a compatibility layer (like Wine, Proton, or Bottles) OR see if Pidgin has a WLM plugin or by default. If you don't know what either of those are, Pidgin is an instant messenger that's designed for use with multiple protocols, meaning you can use Discord, XMPP, IRC, Matrix, Slack, Signal, etc all in the same app. There's also WeeChat, but that's mostly meant for the CLI.
A compatibility layer is a program for running software or games meant for another OS, usually Windows. The main one is Wine and everything else is a fork of or GUI for it. Wine can be buggy but it works better with older versions of programs than newer ones. So you can probably use the original Windows Live Messenger with it if it allows you to change the server. Bottles is basically Wine, but with added features, like analyzing what dependencies a program needs or being able to manually add them. You can find both Pidgin and multiple compatibility layer programs (including Wine) in the Software Manager.