point your cursor on the duelist(Yugi) there will be a list of summons. You will tribute your last summon first i think

Did that answer your question? If not let me know and I will do my best to explain in more detail. But Kumri is right - best way to understand would be to hover over your character and look at the list of monsters you have summoned.

Thanks ! I'm gonna try now and explore with that mechanic to better understand how it works .