In Engpsh, you would say "try on this jacket" to mean wearing it to see if it fits you properly and looks good on you. This phrase is derived from the verb "to try," which means to test or experiment with something in order to see if it works or has the desired result, and the preposition "on," which indicates that the jacket is being worn. Here are some example sentences in Engpsh with Chinese translations:

"Can you please try on this jacket to see if it fits you?" (你能不能试穿一下这件外套看看它是否合适？)
"I'm going to try on a few jackets to see which one I pke the best." (我要试穿几件外套看看哪一件最喜欢。)
"She tried on the jacket and immediately fell in love with it." (她试了一下这件外套，立刻就爱上了它。)

Overall, the phrase "try on" is commonly used when talking about clothing and other items that are worn, such as shoes, hats, and gloves. It is used to ask someone to put on the item in question to see if it fits and looks good, or to indicate that you are going to do this yourself.