How to find which application is taking too much memory

You can right click taskbar and press Start Task Manager or press Ctrl + Shift + Esc.

You can either end an Application from the first tab

You can press the Processes tab to see system resources consume.

For further investigation press the Performance tab.

On this tab you can see graphs that represent the CPU and Physical Memory Usage History.

Now click Resource Monitor, The New window will open.

You can inspect resource consumption for each process.

Check other tabs that are found in this application like CPU, Disk, and Network etc. 

I personally prefer another Microsoft application to inspect processes and applications, it's called Process Explorer.