Inside Job

Inside Job is a Minutemen main quest in Fallout 4.

Detailed walkthrough
Once the signal interceptor has been built, talk to Sturges and step onto the platform. He then asks the Sole Survivor that they infiltrate the the Institute's computer network via a network scanner holotape. The occurring dialogue triggers the quest and starts it.

Once the Sole Survivor is teleported into the Institute, they can move ahead and around a desk with a terminal on it, which faces the elevator that leads down to the concourse. Access that terminal (or any other) and insert the network scanner holotape. Select the option to scan the network, and after the scan is complete, the holotape should automatically return to one's inventory upon leaving the terminal. Exiting the Institute before scanning the network at the Institute is not an option (the relay room doors remain closed). Now, all that is left is to return to Sturges, who is still located at the settlement where the signal interceptor was constructed.

The alternative to this quest is Outside the Wire, in which the Sole Survivor sides with the Brotherhood of Steel and is tasked by Elder Maxson to bring the network scanner holotape to Proctor Ingram. If the Outside the Wire quest is active when Inside Job is completed one is then prompted to talk to Sturges to retrieve a copy of the network scanner holotape, to turn in Outside the Wire by giving the copy to Proctor Ingram.

Bugs

 * Proctor Ingram may not give the holotape back. On PC, a fix is to open the console, click on Proctor Ingram and type "drop 136331 1" to force her to drop it out of her inventory. It is possible for console users to pickpocket to retrieve it..
 * When using an Xbox controller on a PC, the on-screen instructions ask to press X to insert the holotape. The correct instructions are to press A to insert the holotape and X to remove it.