Download the Eclipse Memory Analyzer (MAT) from https://www.eclipse.org/mat/. Select Linux (x86_64/GTK+). Select Download. This will download a file named MemoryAnalyzer-<version>.yyyymmdd-win32.win32.x86_64.zip to your local PC. Extract the zip file. In the extracted folder, double-click the MemoryAnalyzer application. Be aware that it may take a while for the application to launch (perhaps 30 seconds or so).
Once launched, you should get a GUI that looks something like this.