I believe one of the intentions would be that having a senator currently in political asylum and wanted by the US would create a major diplomatic headache for Australia and force their hand at actually addressing the issue of Assange. Until now they've been able to sit back and ignore him because he's locked away in the middle of London as a citizen. If he were to be a senator, that would make things significantly more awkward. I found this [1] interesting analysis of the situation.

As for how voting works:

For the House of Representatives [2], each person is voted in preferential order. Each candidate must be allocated a preference or else your vote is informal and not counted.

For the Senate [3], you may either vote 'above the line' or 'below the line'. Voting above the line involves voting for a party. That party then takes your vote and distributes it amongst the preferences they decide. You cannot indicate preferences above the line - you must vote for a single party and the party then does that for you.

Voting 'below the line' involves marking each candidate from each party. They are still grouped in parties but you may number them in any order, so long as you number them all.

I am not sure what being a party vs. being independent. Independents can be elected to both houses, so I do not quite know what being in a part achieves. The AEC website doesn't obviously offer any information detailing it, at a casual glance.

[1]: http://blogs.usyd.edu.au/cru/2013/04/senator_assange.html

[2]: http://www.aec.gov.au/Voting/How_to_vote/Voting_HOR.htm

[3]: http://www.aec.gov.au/Voting/How_to_vote/Voting_Senate.htm