The Catalan side drew 1-1 in San Sebastian in the second leg to advance 3-1 on aggregate courtesy of last week's 2-0 triumph at the Nou Camp.
That set up an April 19 meeting with Carlo Ancelotti's team at the Mestalla, but Martino reminded his players after the match that there was plenty to keep them occupied between now and then.
"It's a Clasico - that's all I am saying," he said on www.fcbarcelona.cat. "It's very difficult to assess how the teams will be in two months, so first we will concentrate on the games we have before the final.
"There are three objectives this season and we fulfilled one of them (on Wednesday). We completed our objective. These players always play in finals.
"The team played a good match, but we can still play better. We still have time to improve - we can do it for more than 50 or 70 minutes. We could have scored more goals."
Lionel Messi netted the only goal for the visitors, with Antoine Griezmann grabbing an equaliser three minutes from time.
Arch rivals Real advanced on Tuesday with a 5-0 aggregate victory over Atletico Madrid, and Martino acknowledged that meant his team "had the obligation to qualify", adding: "We couldn't miss it."
Wednesday's result saw Barca reach their fourth cup final in six years and offered up the prospect of gaining revenge for Real's 1-0 final win in the 2011 showpiece - secured by Cristiano Ronaldo's extra-time goal.
Spain midfielder Andres Iniesta denied the Primera Division champions would be out for revenge, however.
"I wouldn't say that there are accounts to settle with Real Madrid, but it's a good chance to win another title," he said.