Create Project Web App Instance Project Server 2013:-
Project Server 2013 has the capability to host multiple PWA sites on the same farm.This Web Application will host Top-Level site collection and PWA site.When you are going to Create Project Web App instance(PWA). PWA instance also associates with one content database which was created as a part of your Project Server 2013 installation or New Web Application creation process.[AdSense-A]
To create a Content Database
Step 1: Open your central admin and click on Manage content databases in the section Application Management.
Step 2: Now click on Add a content database.
Step 3: In the Web Application section, choose the Web application where you want to deploy the PWA site.
Step 4: In the DB Name and Authentication section, type the DB server name where you are planning to deploy your Project Web App databases and type a name for the database.
Step 5: Click ok to create Content Database.
it takes some time to create the content database, next step is to create Project Web Application(PWA) site.
To create Project Web App 2013
Step 1: Open SharePoint Central Administration, click Manage service applications in the Application Management section
Step 2: Click the Project Server Service Application On the Manage Service Applications page
Step 3: Click Create Project Web App Instance, On the Manage Project Web app site page.
Step 4: A Project Details or Project Web App page appears with PWA information fields. Fill PWA related information in the field.
Step 5: Click Ok. Your PWA site created.