how do I fix this picture?

The white areas are blown out, there is no information there to retrieve. It's gone.

However - if you have the original raw file available, there is a chance that you can salvage a good part of it. A raw file has a higher dynamic range due to the linear capture, which means that it contains "hidden" highlight data that can be recovered in ACR/Lightroom.

Once it's processed into an RGB file (PSD/TIFF/jpeg), that unused information is discarded.