Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about fixing your eave.
Looking at the photo you posted it seems that a water leak has occurred inside your roof causing the eve to buckle and collapse. Please make sure to cordon off the area to prevent any friends or family members from accidentally walking in this area.
In order to repair your eave, I suggest using James Hardie 2400 x 600 x 4.5mm 1.44m² HardieFlex™ Eaves or James Hardie Villaboard along with Buildex 9 - 10 x 32mm Zinc Alloy 3 Star Head Fibre Cement Screws.
However, before you begin, I recommend locating and repairing your roof leak before attaching the new sheet on your eave.
Please remember to wear personal protection such as gloves and goggles when working on your eave. Please make sure to take all necessary safety precautions when working at height and when dismantling materials under your eave.
If you have any other questions we can help with, please let us know.
I thought I'd add that if the house was built prior to 1980, then unless tested, you should presume the eave sheet could contain asbestos and take relevant safety precautions and wear appropriate PPE including a respirator and disposable overalls. Here's some info on Eaves and asbestos.