From applying Korean patches to converting disc images — written around the parts that actually trip people up.
If this is new to you, begin with How to Apply a Translation Patch. Why there are several patch formats, and what gets applied to what, is the groundwork for everything else.
When you are unsure what the files in front of you actually are, Disc Image Formats is the map — why ISO and BIN/CUE are separate things, and when CSO, ZSO or CHD is the right answer.
Once you know the destination, go to the article for it: Running PS1 Games on a PSP for moving PS1 games to a PSP, BIN/CUE to CHD for tidying files up for an emulator.
When something refuses to work, read Finding the Cause with the File Inspector. Most failures give themselves away the moment you look inside the file.
For handheld consoles and Beat Saber there are Editing Powkiddy Game Lists and Building Beat Saber Playlists.
Everything described in these articles can be done straight away in the tools — nothing to install, no account needed.