On August 12 the Spanish season starts officially with Barcelona against Sevilla in the Spanish Super Cup. However VAR will not be used, like it will be in La Liga.
The first time it will come in is August 17, with opening Liga fixture Girona v Valladolid at 8.15 Montilivi the first time it will be used in an official game in Spain. Even if the Super Cup was two legged at Camp Nou and the Pizjuan, rather than being one match in Tangier, VAR would not have been used.
The deal to use VAR was signed between the RFEF and La Liga. If it all goes well this season, then it might be used in other competitions from next season - it might also be used in the Segunda from 2019-20, when all the stadiums have equipped themselves with the right tech.