Built into the last update to SigmaStudio is a new properties box for E2PROMs that allows the user to set various properties. Here is a screen shot of the window. If you are using a 24AA256 EEPROM, you will need to set the parameters to:
Memory Size: 253952 bits
Page Size: 64 byte
Write Speed: 100 kHz
Number of Address Bytes: 2 byte
For other EEPROMs, please consult the datasheets for both the Analog Devices part and the EEPROM.