Create an Excel Services service application - SharePoint 2013

a)   On the Central Administration home page

b)   Under Application Management

c)   Click Manage service applications.

d)   On the Manage Service Applications page

e)   Click New, and then click Excel Services Application.

f)    In the Name section, type a name for the service application in the text box.

g)   Select the Create new application pool option and type a name for the application pool in the text box.

h)   Select the Configurable option, and from the drop-down list, select the account that you created to run the application pool.

i)     Click OK

Excel Services trusted data connection libraries - SharePoint 2013

a)   In the SharePoint Central Administration website,

b)   In the Application Management section, click Manage service applications.

c)   On the Manage Service Applications page,

d)   Click the Excel Services service application that you want to configure.

e)   On the Manage Excel Services page,

f)    Click Trusted Data Connection Libraries.

g)   On the Excel Services Application Trusted Data Connection Libraries page,

h)   Click Add Trusted Data Connection Library.

i)     On the Excel Services Application Add Trusted Data Connection Library page, in the Location section, type the address of the trusted data connection library in the Address box.

j)    In the Description box, you can also type a description of the purpose for this trusted data connection library.

k)   Click OK.