In Vim, you can change multiple lines in a few different ways. One way is to use the "V" command in visual mode. To do this, first position your cursor on the first line you want to change, then press the "V" key. This will enter visual mode and highlight the line your cursor is on. Now, use the arrow keys to move your cursor down to the last line you want to change, and press the "d" key. This will delete all of the lines you have highlighted.
You can also use the "cc" command to change multiple lines. To do this, first position your cursor on the first line you want to change, then press the "cc" keys. This will enter insert mode and allow you to change the text on that line. Once you're done, press the "ESC" key to exit insert mode, and your changes will be saved. You can now use the arrow keys to move to the next line you want to change, and press the "cc" keys again. Repeat this process until you've changed all the lines you want.