Question

One of the main ways spain began to unify was?

Answer 1

Since you provide no options,

The event that marked the unification of spain was the marriage of Ferdinand of Aragon and Isabella of Castille  in 1496.

their marriage set the stage for the Creation of the Kingdom of Spain

hope this helps

Answer 2

One of the main ways Spain began to reunify was by

Answer: Accepting Muslims and Jews and their religious beliefs. 

It was the unified state who was successful in driving the Muslims from Spain and in bringing religious unity to Spain by persecuting and driving out non-Christians.

I hope it helps, Regards.