在我的android工作室中没有显示Android设备

我最近下载了android studio 2.3.3。我是java编程的初学者，在使用IntelliJ IDEA进行编程练习后，我正在进行app构建。我正在学习使用视频课程，在视频中，预览中会出现一个Android模型。当我下载它时，没有安卓，只有一个箭头。我尝试在设置中进行更改但没有工作。我不知道为什么会这样，但我猜它正在发生，因为zip文件有问题。如果我得到一些帮助，我将不胜感激

I recently downloaded android studio 2.3.3. I am kind of a beginner in java programming, and I am proceeding with app building after some practice in programming using IntelliJ IDEA. I was learning using a video course, and in the video, an android model appears in the preview. When I downloaded it, there is no android showing, just an arrow. I tried making changes in the settings but none worked. I don't know why this is happening, but I am guessing it is happening because there is a problem with the zip file. I would appreciate if I got some help