CAD can be opened through the following steps: 1. Open the CAD software. 2. Select the "Insert" tab on the main interface. 3. Select the Browse option in the Tiles panel. 4. Find the required CAD file and double-click to open it. 5. In the pop-up "Insert Reference" dialog box, select the required object and insert it into the current drawing. Note: When opening a CAD file, you need to ensure that the file format is compatible with the CAD version.