Find an interesting open source project with active and friendly maintainers (this might take a bit of looking). Figure out how to check out and build the code,

Find an interesting open source project with active and friendly maintainers (this might take a bit of looking). Figure out how to check out and build the code, then choose an open bug and fix it (or find a small open feature request and implement it). This will require learning how to read code in a bigger codebase and make targeted changes, which is basically the first thing you need to be able to do as a software professional.