I have installed a new ignition on y aprillia pegaso 2008 and it wont accept the code numbers

It's not the new switch, it's the new keys that have to be programmed.
The keys have uniquely coded chips in them, when you turn on the ECU uses the antenna that is by the ignition switch to look for a code that it recognises, you need to introduce the new key codes to the ECU.
This is what the manual says:

In case of installation of a new ignition switch the procedure is as follows:
Turn ON using new key
The dashboard will not recognise the key and will ask for the customer code: insert the customer code. It is 00000 when supplied. It can be changed to any numeric five digit number.
Now you can enter: MENU, DIAGNOSIS (insert the service code 25973),
Then select MODIFY KEYS and implement the procedure.

If you are not sure about the mode switch, this is what you do:
Use handlebar "mode" switch (left / right) to select "Menu" option on the screen, then press mode switch in to enter.
Use handlebar "mode" switch to select "Diagnosis", press to enter.
Use handlebar "mode" switch to enter the workshop code (25973).
When you have selected the digit you want then press in and it will move to the next digit etc.
You can't screw anything up, if you do it wrong go back or turn off and start again.