I need directions on how to do this. This is not a duplicate question. As the answers given in the links before are all outdated and from either 2012 or an Xcode that doesn't support this format. I need steps that are currently working for this model. In my App store there is only insanely high updated versions of Xcode so idk.
Go to Apple Developer and log in with your Apple ID. Then open See more downloads near the bottom of the page. Search for Hardware and download Hardware IO Tools for Xcode 7.3. The Hardware IO Tools for Xcode 6.3-7.3 all contain the same Network Link Conditioner 2.0 pref pane which should work at least in 10.9-10.11. The newest IO Tools are still recommended because AFAIK they contain newer certs.
Open the downloaded dmg, double-click and install Network Link Conditioner.prefPane for all users.
Open the pref pane in System Preferences and determine an appropriate UL/DL speed.