Find a Gallimimus egg or spawn a Gallimimus in the Fossils and Archaeology mod
If using an egg, place it in a suitable nesting area and wait for it to hatch
Keep the hatchling in a fenced, protected enclosure
Feed the Gallimimus the correct food item for the mod version you are using
Continue feeding it until it becomes tamed
Use the mod’s interaction item, if required, to claim or imprint on the Gallimimus
Check the creature’s behavior to confirm it is no longer hostile or wild
Keep it enclosed until fully grown and stable
Use a lead or pen setup to transport it safely after taming