How do i know when the ticket will come through the post to me?

Basically i ordered this ticket online to go see Wiz Khalifa live at O2 ACADEMY in Bristol, i ordered it on the actually website of O2 ACADEMY as well. i gave all my details like my card number, my address and all that and it emailed me confirming my purchase but i'm not to sure when the ticket will arrive tbh? i ticked the UK post box when it asked me how i wanted it to be given to me and i'm not sure when it will arrive, i need advice now guys! although the consert is in November but still, when the hell does the ticket come to me?