How to join a custom server on Mc [bedrock]?

[jenos99 0]

So I’m kinda new to joining severs and stuff but I’ve been having trouble joining friends servers like I don’t understand what whitelist is and all that stuff but he said he put me on that and that I should be able to join but when I go into Minecraft and try adding the server appvalley tutuapp tweakbox, it just doesn’t work (only happens with custom servers/ Friends servers) and I tried watching yt vids about it but I still don’t really understand it (I plc Mc on a pc) pls help😊