A mold is the negative of a shape that you would like to make. You can make a cast of an object you would like to reproduce by sculpting two pieces of clay around the object. When the clay dries, remove the two pieces. If you fill each half with the liquid plastic and then put the halves together, you can make a copy of that object. You can also use a cookie cutter to cut shapes out of the plastic while it is still warm. An alternative to making your own mold, is to purchase a mold at a craft or hobby shop. Once you have a mold, you can use it to make more objects. While the plastic is still hot, pour it into the mold. Make sure that the plastic gets into the entire mold and try pop bubbles by lightly tapping the mold on the counter. To make the object easier to remove when it dries, coat the mold with a non-stick spray before pouring the plastic in. The plastic will take a few days to dry and fully harden. The amount of time it takes to dry is dependent upon the thickness of the object. If the object is very thick, it can take longer than two days to fully harden. After two days, check the plastic. If it still appears to be wet, let it sit for another day and check it again. Continue to do this until the plastic is fully dry. After waiting a few days, the plastic will be fully hardened and dry. At this point, you can remove the plastic from the mold. You have now made your own plastic version of whatever object you chose to mold. You can reuse this mold to make as many plastic versions of the object as you like.

TL;DR in Chinese:
制作塑料的模具。 把热塑料倒到模具里。 把塑料放干至少两天。 从模具中取出塑料。