Melbourne

First, measure the space where you want to put the art. This could be one big pic or several small pics. Your choice. Make purchase(s) as per your preferences and the space available. Given the huge white space in the photo - my preference would be for 3 smaller pieces, but you do you. Maybe one medium size and two smaller ones. This is def your choice and preference. If the sun shines directly on that wall, don't buy prints as the reds will fade fairly quickly.

There are art shops like the Picture Gallery. Also markets like Ceres/Fairfield often have booths for local artists to sell their creations. Also the Saturday Rose St art market in Fitzroy. With xmas coming up, every artist in Melb is looking to downsize their stash of finished works at a profit. Check out opshops like the Brotherhood or Vinnies for cheaper options. Some surprising gems can turn up there. This can be a fun thing to do on a weekend.

You will also need :

1. The actual piece(s) of art.
2. A way to attach/hang the art. Do you want this (or is it required) to be removable when you move out? I think the rules have changed recently for rental properties, and you no longer have to erase any signs that you've hung a picture. So you can consider nailing a picture hook(s) to the wall, and are not limited to those removable stickytape backed hooks that fall off if the temperature goes over 30. Be aware that using double sided tape can remove paint from the drywall, which will need to be rectified when leaving. Attachment/hanging will depend a bit on how heavy/large the piece is - Bunnings DIY online may help.
3. A piece of news/brown/wrapping paper (cheap xmas paper is everywhere rn) cut to the size of each art piece. Some painters tape or masking tape cut into small sections.
4. A tape measure of some sort and a pencil.

Position cutout(s) on the wall using the painters tape until you get an arrangement you like. Use pencil to mark where the corners should be, and the top of the item. Use the tape measure to find out how far down from the top mark you'll need to put the attachment point. Fix that to the wall. Hang art. Check the corners line up with pencil marks then erase the pencil marks with a small piece of fresh bread or a regular eraser. Job done.

There can be of course a fair bit more to it than this summary - consult youtube for one zillion how to do it videos. Some of them are even accurate.