There are two ways to form future tenses.
The one you describe is for imperfective verbs, like "Показывать". "Я буду показывать"
The one used here is for perfective verbs, like "Показать". When you conjugate a perfective verb like the present tense, it functions as a future tense.
Maybe someone could explain better than I can, but the basic outline is:
Imperfective verbs describe actions that weren't completed or may not be completed. Or they happen multiple times.
Perfective verbs describe actions that either were completed, or are expected to be completed. And only happen once.
Most verbs come in pairs of imperfective and perfective. There's no exact rules for how an imperfective would differ from its perfective counterpart or vice versa. Some just attach an "По-", some add an extra syllable, some are completely different, like "Говорить"(imperfective) and "Сказать"(perfective).