Make a folder in sourcemods and name it my mod then I copy the client and server dlls from the hl2 bin folder and create a bin folder in the root of my mod and paste the dlls then in the root of you’re mod folder you make a models folder a scripts folder a maps folder a CFG folder a materials folder then copy the gameinfo.txt from half life 2 and edit it to change the title to the title of you’re mod and that should be the basic setup now look up anything else you need like making a main menu background etc if you want to make any code changes you will need the source SDK 2013 code but if you’re just using base assets my method is good enough
But like the other guy said you’re best friend is google for this stuff I haven’t even covered a percent of what you can do