There are a number of options available for learning to weld.
TAFE is always a good starting point for beginners through to certificate level.
Options will of course depend on, your location, access to a training establishment and level that you want to achieve.
Another pathway would be to apply at an engineering/welding workshop as a beginner.
If you are at the DIY hobby level, there are YouTube videos and various welding publications available to get you started.