Question

what does the bold appositive phrase refer to? a famous soccer player, heiheis friend signed my world cup poster.

Explanation:

An appositive phrase renames or identifies the noun it is adjacent to. In the sentence "A famous soccer player, Heihei’s friend signed my World Cup poster", the bold appositive phrase "A famous soccer player" is used to identify or rename "Heihei’s friend". So we analyze the relationship between the appositive phrase and the noun it modifies.

Answer:

The bold appositive phrase "A famous soccer player" refers to "Heihei’s friend".