The cards go in the IIe's Auxiliary Slot, which exists in addition to the seven standard Apple II peripheral slots present on all expandable Apple II series machines.
Therefore the user can enter 80-column mode by issuing the command PR#3 or IN#3 in the BASIC prompt.
[3] The "extended" version of the card features a jumper block (J1) that when installed enables the double high-resolution capability.
Since early "Revision A" Apple IIe motherboards are incapable of supporting the bank switching needed for the enhanced graphics mode, the block needs to be removed to disable the feature.
Soon after the release of the Apple IIe, 80-column text support became a basic requirement of many software packages.