How to add a section In an EXE

I don't know how to explain it detailedly ,just like this:

0001: PUSH EAX
0002: DEC EDI
0003: INC EBP
.
.
I want this:

0001: PUSH EAX
0002: JMP 0008
0003: INC EBP
.
.
.
0008: NOP
0009: DEC EDI
0010: JMP 0003

============================

Begin 0008 is the added section, use PEeditor can add a section, someone told me it needs change the ImageSize at the same time,PEeditor also can do this. But I failed.When I use OllyDbg open it , I was told it's not a valid EXE file.

Thank you very much for guidance.