Bandcamp is sending their sales information to Official Charts on Friday mornings and to ARIA on a daily basis.
To be chart eligible, you must enter UPC (bar code) information for albums and ISRC information for tracks when you set up your release. Enter this info on the edit pages when you’re uploading artwork, adding lyrics, etc.
Also, in order to count toward Official Charts in the UK, albums must sell for at least £3.75 GBP and tracks for at least £0.40 GBP (or the equivalent in your band’s currency). ARIA Charts do not enforce any particular minimum price, but they do require the album or track be purchased in order to be counted.
You’ll find more info on chart eligibility here: https://bandcamp.com/help/charts