curious about Harvard

Hi… i’m a new member and i’m thrilled to have found this U.S. site.
I am in second year from the University of Sydney(Aus), and have graduated from a examination-admission high school.
This is not to say I am smart but I would like to apply for Harvard in my later years.

A problem is that I have been quite inconsistent with my grades in my final years of high school and my first year in university(failed at half my subjects) . Considering my degree only takes three years I am worried that my academic transcript would be a major obstacle in gaining enrance.

I would like to know the importance of these academic transcripts in application consideration and if there are other ways in which I can make up for this.
Thanks.