Hi Every body , i want to customize the creation user webform in FIM portal , can some help me please ? 

1. Extend service schema, add attributes you want that do not exist already in the current schema

2. Bind the attributes to person object

3. Export the RCDC for user creation

4. Edit the RCDC you exported; add, remove, modify the attributes and their properties. Change tabs as you want them to appear on your form.  This is a simple XML File, open with Visual Studio or some editor that is easy to read

5. Import the RCDC back

6. Do an "IISRESET/ NO FORCE"

7. Grant access to the right people, via MPRs on the attributes added

Have a nice day!

Hello

Nosh described the correct steps to do, in Addition here are some links the might help:

https://technet.microsoft.com/en-us/library/ee534918%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

https://technet.microsoft.com/en-us/video/creating-a-custom-rcdc-in-forefront-identity-manager-2010.aspx

http://blogs.msdn.com/b/connector_space/archive/2014/12/01/rcdc-session-0-understanding-rcdc.aspx

-Peter