I use proteus 6.2 sp5 to make my schematic diagrams.I am new to the program. I wanted to ask what should I do about devices which are not available in the library. For example ULN2803 is not in my library but ULN2003 is. How can I add ULN2803?
Yup - you can create your own schematic parts, PCB footprints and simulation models.
The first two are documented in the help files whilst the latter is in the SDK. You can also request development direct from the Labcenter peripheral modellers provided that the part is general purpose enough to be of use to the customer base.
Finally, ULN2803 is both present and modelled in the latest release of the software.