Choose plain or fancy, as required. Cut it to the length required if it's not already done. Mark the position with a pencil. Use a tape measure to mark the position of the other bracket at the opposite side. Always check for electrical wiring or plumbing before drilling. It's also wise to place a drop sheet on the floor to make it easier to collect the drill dust.  Use a masonry drill bit.  Drill to the depth that the screw requires to penetrate the wall sufficiently. Insert a wall plug. Attach the screw (or screws) by screwing them in as far as they will go. Hold the board in place with one hand. Then, using a spirit level, hold the board across to the other mark you made earlier to check that the board will be sitting evenly. If the mark appears accurate, it's ready, if not, make adjustments as required. Follow the directions given for the first bracket. Lay the board across the brackets and screw it to them from the underside. Be sure to use screws that will not penetrate through to the other side of the board; they must remain wholly inside the shelf board. Gently press on the shelf to check that it is firmly attached to the wall. Make sure that your shelf can bear the weight of heavier objects and don't put something valuable on your home-made shelf until you know that it's secure.

TL;DR in Chinese:
选择一对支架。 选择搁板。 按照你希望的格架在墙上的位置，将支架在墙上扶稳。 按照第一个支架在墙上标记的位置，在墙上钻出固定支架所需的眼。 将支架在墙上装稳。 将搁板放置到支架上。 在墙上为另一端的支架钻眼。 将搁板放到支架上。 收起地板铺的报纸，倒掉钻出的粉尘。 完工。