You can use find. To search the current directory for a file called foo.txt:
find . -name foo.txt -print
If your slocate database is up to date, you can also use slocate
To make sure slocate is up to date, you need to run updatedb as root:
Find will take longer, but will be more accurate than locate, since locate is using a database that may be several days old. If the file has recently been created, use find, or run updatedb (Takes a long time...) before using locate.
I hope this helps