someone explain how to make a n enchantment table?

each enchant eats lapis too, 1 to 3 depending on the option, so bring a stack. and the level 30 slot only actually takes 3 levels off you - you just need to be sitting at 30 to pick it.

1 book, 2 diamonds, 4 obsidian. book top middle, diamonds either side of the centre, obsidian in the centre and the whole bottom row. the table on its own only gets you low level enchants though. you want 15 bookshelves around it with a one block air gap between them and the table to unlock the level 30 options. anything in that gap, even a torch or carpet, blocks the shelf.