git - Once a file extension is added to .gitignore how do I remove its files from the untracked files list? -

visual studio has new intellisence database file , when ran git status found it

on branch master branch up-to-date 'origin/master'.
untracked files:
(use "git add ..." include in committed)
serversidecode.vc.db

like predecessor, *.sdf, can added .gitignore. edited .gitignore include *.vc.db. when run git status see:

on branch master branch up-to-date 'origin/master'.
untracked files:
(use "git add ..." include in committed)
serversidecode.vc.db

what additional step, beyond adding file .gitignore file, need in order ro remove file list of untracked files returned git status?

(n.b. realise run git status -uno want know additional step required ignore new file types added .gitignore file.)

after adding extension .gitignore should no longer show in git status. sure there's no typo in .gitignore, , file placed correctly?