Please follow the below steps:

1) Login to PleskCP.
2) Click on Home.
3) Click on Domainname.
4) Click on Web Applications
5) Click on Install New Application
There you will find the application list
6) There is an Install tag in front of each application. Click on it which ever application you want to install.
7) It will ask some details. Please give the details properly and complete installation.

Note: If you face any issue please raise a ticket from client/member area.