Installing plastic on your drafty windows does really help with cold drafts.
If you do have cold drafts coming through your windows try to find out where the cold drafts are actually coming through the window from.
if there's any air leakage take some caulking and seal those air leaks up which also helps.
You can use a candle while lit and move the lit candle around the window where the drafts seem to be coming from and then seal those areas or just seal the whole window with caulking.
Then put the plastic shrink wrap on the windows and use a hair dryer to shrink the plastic until it's tight.
I have used the plastic shrink wrap on my old drafty windows in winter and it really did help until I could buy and install new insulated windows.
Installing a blanket over the windows or an insulated curtain over the windows can also help keep out cold drafts and reduce your heating bills.