$ locate /.DS_Store
[download]

and then again (because it's cheap) to clear the files:

$ locate /.DS_Store | xargs rm
[download]

find can do the same, without needing a possibly outdated database:

find / -name .DS_Store -type f
[download]

(-print is implicit, -type f restricts to regular files)

And then, to avoid various traps with "funny" path names, pass found path names around ASCII-NUL separated:

find / -name .DS_Store -type f -print0 | xargs -0 rm
[download]

Or invoke rm directly from find:

find / -name .DS_Store -type f -exec rm \;
[download]

(Backslash or quotes around the semicolon are needed in bash)

The same, but be smarter (like xargs, collect arguments instead of invoking rm for every single file):

find / -name .DS_Store -type f -exec rm {} \+
[download]

(Again, backslash or quotes around the plus are needed in bash)

Or have find delete the file without forking a separate process:

find / -name .DS_Store -type f -delete
[download]

Optionally show what is deleted while deleting:

find / -name .DS_Store -type f -print -delete
[download]

Alexander