How to convert a circuit into a single ic/part in orcad pspice

Generally, you remove all of the sources. You are using 74x and 54x parts so you may not be too concerned about running from a "fixed" supply voltage and may want to keep some VDC parts that set bias / threshold levels but keeping the connections to your A, B and INH inputs fixed might not be too flexible for "general" use. Connect Ports to the nets for input and output terminals, PSpice uses Place>Hierachical Port to define these, strictly these ports "have a sense of direction" but, for this purpose, the direction type is ignored. Once the sources have been removed and the I/O ports added, select the DSN file entry in the Project Manager window, if you have a "default" schematic folder name of "SCHEMATIC1" you might want to rename this to something more suitable for your model, note that the name needs to begin with a letter and not contain any spaces, and use Tools>Create Netlist, go to the PSpice tab, check the box for "Create SubCircuit Format Netlist" and specify a name for you LIB file, like "decoder.lib" and pick a location to find that file from for the next stage. Assuming that the LIB file gets created correctly, start the Model Editor, use Capture as the schematic tool if you get a choice, and use File>Open to open the LIB file you just created, use File>Save to add the PSpice "marks" to the LIB file to delimit the models (not an essential step), then File>Export to Capture Part Library to create a default symbol for the part - this will create an OLB file if all goes well. (You can edit the default graphical symbol if you File>Open>Library, open your OLB file and double-click the graphical part to edit.) To use this in another design, add the OLB file through Place>Part, Add Library icon, so that the graphical symbol(s) can be placed in the schematic page and Edit the Simulation Profile for the project and add the LIB file through the Configuration Files tab and Library selection, use the upper Browse button to locate the LIB file and use Add to Design as the best way to configure the simulation library.

Generally, you remove all of the sources. You are using 74x and 54x parts so you may not be too concerned about running from a "fixed" supply voltage and may want to keep some VDC parts that set bias / threshold levels but keeping the connections to your A, B and INH inputs fixed might not be too flexible for "general" use. Connect Ports to the nets for input and output terminals, PSpice uses Place>Hierachical Port to define these, strictly these ports "have a sense of direction" but, for this purpose, the direction type is ignored. Once the sources have been removed and the I/O ports added, select the DSN file entry in the Project Manager window, if you have a "default" schematic folder name of "SCHEMATIC1" you might want to rename this to something more suitable for your model, note that the name needs to begin with a letter and not contain any spaces, and use Tools>Create Netlist, go to the PSpice tab, check the box for "Create SubCircuit Format Netlist" and specify a name for you LIB file, like "decoder.lib" and pick a location to find that file from for the next stage. Assuming that the LIB file gets created correctly, start the Model Editor, use Capture as the schematic tool if you get a choice, and use File>Open to open the LIB file you just created, use File>Save to add the PSpice "marks" to the LIB file to delimit the models (not an essential step), then File>Export to Capture Part Library to create a default symbol for the part - this will create an OLB file if all goes well. (You can edit the default graphical symbol if you File>Open>Library, open your OLB file and double-click the graphical part to edit.) To use this in another design, add the OLB file through Place>Part, Add Library icon, so that the graphical symbol(s) can be placed in the schematic page and Edit the Simulation Profile for the project and add the LIB file through the Configuration Files tab and Library selection, use the upper Browse button to locate the LIB file and use Add to Design as the best way to configure the simulation library.