Arrival records

As a relative newbie to all this, can anyone tell me where to find records of arrivals into Australia (preferably online search facilities)?

I am trying to find information about my ggrandmother, Maggie Boswell. I know that she was born 02-05-1871 in Rutherglen to parents Jonathan Boswell and Ann Hart Miller.

She had siblings Annie Hart - 07-09-1863 George - 08-01-1866 Isabella - 30-08-1867 John Miller - 06-08-1868 plus 1 Frederick - 08-03-1873

She married William Keal on 27-06-1894 in Toowoomba, Queensland. William arrived in Brisbane on 21-07-1888 on the ship "Waroonga" with his brother George.

I can find no information about her arrival into Australia, and my father says whilst he remembers his grandmother, he doesn't remember any other family from the Boswell side.

There is also some question about William and Maggie's two eldest children, Ernest Alfred 06-08-1891 and Walter Chris 12-02-1894 both born prior to the marriage. The family always wondered if they were the sons of William or if Maggie had them when she met William. They went on to have 6 more children, my grandfather being the youngest, born 11-01-1904.

I know that Maggie died 24-08-1955 and is buried with William in Toowoomba & Drayton Cemetary, having been there recently and photographed their grave.

Can anyone help with information about how and when Maggie arrived in Australia? Or tell me where I can search for that information?

Any buttistance would be greatly appreciated. David