open layout tool
1)than go to tools--> library manager
2)when the library manager opens select the component in which u want to make changes
3) select the pad which u want to change and right click properties
4)check which padstack is used ie the padstack name
5) go to spreedsheet and select padstack.
6)navigate to find the required padstack name
7)there is option pad shape in the padstack spreedsheet u can double click on the circle pad shape to opean a menu now there are diffrent pad types given u can select and change any other parameters u want.
save and refresh.
this is the method to change the pad shapes
or u can even create new padstack
thanks