If you know nothing about the process of recovering a damaged database and that database is valuable, hire someone. This is not a great DIY or Do It Yourself project because it is possible to lose data.
If the data in the database is not valuable, then check out DBCC CHECKDB and read up on the process at other sites too. I'd recommend SQLskills.com | Immerse Yourself in SQL Server as a good starting point.
In theory, theory and practice are identical. In practice, theory and practice are unrelated.