OP, curtains can help and I do not know the product you have ordered but would like to point out that the smaller the room the more you need absorption and that absorption needs to be broad-band in performance.
Usually 4" thick frames are used to house 2" thick fiber panels with a 2" air gap behind. Curtains will absorb over a much narrower band and therefore not as effective. Perhaps you can use what you have in conjunction with some more curtain.
What I have done for some, especially those with wife with scowling face, is to use a multi-track curtain-rail system that allows to hang 2 or preferably 3 curtains. This will look the same although be a little more bulky. The fact that they are physically separated will broaden their frequency of absorption.
It would help further if you placed some absorption on the opposite wall if possible.