@Frank I think for most successful new testers the testing mindset usually precedes a lot of the technical skill depth. When I talk to people starting their testing careers one of my go-to speeches can be summarized as "The only difference between complaining or discussing an application vs testing it is how clearly and thoroughly you document the actual outcome and expected outcome of problems as you encounter them". Many people are able to navigate around applications and look for problems but testing is really about turning these findings into actionable tasks for your development team and that's where effective communication is so critical.
A rampup for many brand new testers will look like this...
1) When the application doesn't do what you expected, practice both speaking and writing what you did, what you expected the application to do, and what it actually did. If you have a friend who wouldn't mind reading your results, see what parts are or aren't understandable to them and focus on improving areas of misunderstanding in the future.
2) As you get more comfortable communicating your findings and your understanding of the application grows, you can communicate even more effectively if you're able to expand or refine your vocabulary. Much of this (ex: development, UX, design terms) will be common vocabulary for most software shops but some might be specific to the application you're testing. Pay attention to how your peers talk about the application under test and try to be clear and consistent with their standard terminology.
3) Look for ways your can include even more information about your testing results. This may be the use of screenshots, video, application logs, information from Dev Tools or other ways to see a little under the hood. This will become especially important as the complexity of your testing targets and their business requirements grow.
4) Figure out how to test more/faster in the specific situation you find yourself in. Usually this will eventually involve channeling your new-found ability to understand and describe the application and turn it into test automation or scripts that reflect this understanding.