Right-click on References and select Add Reference..., navigate to the to DLL and presto ... you're done.
Right Click References -> Add Reference -> Wait forever for the list to load -> Browse -> Select your Dll
Then when it has been added to the reference list, set it to Copy Local (if it is not already). This will put it in the output folders for you.
Right click on the "References" folder in the list and choose Add reference. On the Browse tab, browse to the directory containing your project, and the subfolder. Select the assembly and add it to the project.
or right click on the project in the solution explorer and select 'Add reference', then you can browse to the file, as the other answers have indicated
Try the following
- Right cilck on the References Node
- Choose "Add Reference"
- Click on the Browse tab
- Navigate to the dll MySql.Data.dll on disk and hit OK
Once it's added, click on the reference under the References folder and hit F4. This will bring up the properties tool window. Make sure it is set to "Copy Local" = True. This will ensure it gets deployed with your application by the standard installers (MSI and ClickOnce)