Click on File at the top left of the Blender UI, then Append. Navigate to the Brushes .blend file and click it. Locate the Brush folder. Click it. Now chose which brushes you want to add to your project. (Tip: Hold Control to Append multiple brushes at once.) Click on Append. Now your brushes should show up in the "N" panel under Tool tab/ Brush Asset. Click on the Icon to choose different brushes.