I wrote a longer answer to a similar question long ago, but I can't find it anymore, so briefly:
- Good job contributing to open source! It's a great way to learn and it helps the community.
- Sometimes repositories have a label "good first issue" or "beginner issue", or they organize such issues in another way. If that doesn't work, maybe you could check some issues and try to pick the most accessible one.
- Frameworks are usually pretty big and use fairly complex code to do what they do. You might have a much easier time getting started on a smaller, non-framework project (it could still be something that uses Vue).
- If you want to work on an issue, you could leave a comment to ask for help. It might not work, people are generally quite busy, but it's not rude to ask. You could either ask for some hints on where to start, or some specific questions on what you're unsure about. Don't just say "I need help".
- If you want to help the project, there are many ways other than code: documentations, tutorials, finding bugs, ... If you want to practise programming this won't help, though.
- If you're unsure about how to interact on Github, several people have written blog posts on Hashnode about that, might be useful to check that out.