Salman,

As requested here are the steps.

Step using Export/Import to excel for multiple resources into Primavera
Note:
Before you can assign resource to a project using export/import to spreadsheet (xls) facilities all resources must created first. (You can use Excel SDK for this or manually define it under Enterprise-> Resource)

1) Open the Project to export then export template first. Select File-> Export then tick Spreadsheet (xls) then click Next.
2) Under Export Type tick Activities and Resource Assignment then click Next
3) Tick the Project to Export then Click Next
4) Click Add to add a template or click modify to modify the existing template.
5) Under the Subject Area textbox select Resource Assignment
6) Select only this field and remove the rest. (Activity ID, Activity Status, Resource ID, Roles ID, Cost Account ID, Budgeted Units, Remaining Units and At Completion Units) then click Ok then Next
7) Click Select Excel file textbox and change the destination folder and filename then click next then Finish
8) Open the exported excel file. (You should have 3 tabs named TASK, TASKRSRC and USERSDATA)
9) Don’t modify USERSDATA as it contains the usersdata and setting of the project exported.
10) Click TASKRSRC tab and start entering the information required or data to upload. (explained below) (Note: 1st row contained field name of a table and 2nd row contained brief description of field)
• Activity ID – Enter Activity Id where you resources will be assigned (TASK tab will contain all Activity ID and description for your reference and you can copy and paste this to TASKRSRC worksheet including Activity Status)
• Resource ID – This are the resource id created in Primavera as I explained on the Top. Enter corresponding resource id to activity (Note: Resource Id must be the same as defined in Primavera)
• Roles & Cost Account ID (leave it blank if you did not assign any otherwise enter if assigned)
• Budgeted Units, Remaining Units and At Completion Units – Enter all with the same data (Note: It’s more reliable to update all three fields instead of budgeted Units only because some import may update budgeted units only but remaining and At Completion Unit may remain zero (0) because of the setting and the way it was imported)
11) Save the excel file then go back to Primavera and Select File->Import from the menu. (You can leave excel file open or close if in doubt)
12) Tick Spreadsheet (xls) then click Next.
13) Click … button and select the excel file that you modify and save then click Next.
14) Tick only Resource Assignment then click Next.
15) Click Import to textbox and select the project then click Next then Finish.

If the all data entered to excel is correct you should get a message import successful. Check the project and you should have all the resource entered.
Note: I recommend trying 1 or 2 activity first before going for the whole data to familiarize the process first and how it works.

Caution: if assigned resources is existing on that activity id but roles is defined or cost account is defined on the existing but not on the new assignment, import will not update the existing resource instead it will add a new assignment specially if the setting on resources tab-> Resource Assignment (Resource assignment can be assigned to the same activity more than once) under Project module is tick. Also make sure that there is no duplicate resource id which is possible in P6 resource under different level on hierarchy. It may assign different resource than the intended resource.

Salman,

You can use the export/ Import to spreadsheet (xls) facility to add multiple resources with value. I believe I already explained how to use this on other post.