You have assigned personName to be a double. But a persons name, such as "mike" is a String. So when you say personName = prompt.nextDouble(); the program is expecting a double but you are feeding it a String.

So change that line to personName = prompt.nextLine(); ..and

At the top where you have double weight, height ..etc remove personName and on a new line below it write

String personName;

I hate it when people put tiny things like that up. Just copy and paste the code into the post.

I don't understand how to make this dang thing work. The program runs and everything, but when the prompt asks me for my name, and I type in a name, it gives me that red error at the bottom.

Here's a photo of what I'm talking about. Just click on it to zoom in. http://postimg.org/image/f2hg0f1af/