resize file system using omv 5 webgui

hello, this may be a stupid question but:

i had a single 1.5tb drive for data. a few months ago it died.
I bought a new 4tb drive, cloned from an offsite backup stuck it in and all was good.
but... it's cloned. so it's still only 1.5tb
how do i make it 4tb?

i went into omv webgui and clicked on physical disks. it's 4tb in there
I go into file systems and it says capacity 1.5
if i select it and click on resize i get a warning up that says

Zitat

Do you really want to resize the selected file system? You have to do that after a RAID has been grown for example.

i click yes but nothing happens.

have i misunderstood what this funciton is for?

the machine itself has no cd rom drive and is in the garage so its hard to get to physiaclly (but i can ssh ok).

thanks David, will do.
Thanks again for the prompt response.