Tools menu > data driver > select sample inputs in 
automation program > click parameterize options icon to 
select XL sheet coloumn name > click "OK" > Click finish


once you are well familiar with QTP then directly in the 
test pane you can write 

set datatable("column name",dtglobalsheet/sheetid)

I'll take an example of login screen and explain.
first record the login page.
u  can see the recored script in the expert view.
Browser(" WWW").Page("ABC").webedit("").set "XYZ"

Know if u want to parameterize username one can do it 
manually by writing script in the expert view or using 
wizard data driver, under tools menu click on datadriver
in the wizard select datatable as parametertype and in Name 
and u can select the location as well global or localvalue 
field u can change the name give Username and click ok 
username will be added to datatable as column name under 
that u can give diff values then run the script.this is 
using data table.parameterization can be done using 
environmental var and random numbers aswell.
validations can also be done with parameterization
various methods u can apply.