You can use the current valid Schengen visa. It is not required to reopen a visa.

If the visa is currently valid, and there is in reserve the number of days required for a stay in the Schengen area , then with it you can enter Spain without any restrictions.

To make such a trip you need to prepare the following papers: financial guarantees for the entire period of travel, return air ticket, medical insurance, and an invitation from friends. The last is made in free form (preferably in Spanish), but it must include the personal and contact details of the inviting person.