The Glebe Liqour store is on the corner of Forsyth St and Glebe Point Rd. It's not far from Wigram Rd which is where you can catch either a 431 or 433 bus to, then just walk a little further down Glebe Pt Rd and it is on your right.
There is parking available on Glebe Point Rd and you can usually find a spot, while you grab what you need, on Forsyth St - even during the day!
The light raill is another handy alternative to get to Glebe from the City.