I can't write your full homework, but I can give you some information to guide you!!!
1) the introduction - it should include a statement such as "my favourite sport is... and I will explain the reasons for this opinion in the following essay"
2) then in the body you give those reasons. For example, you could write "I like skiing because I am good at it" or "I like football because I am good friends with the other members of my team"
3) then you repeat the main statements of your essay in the conclusion.
