Another way to do to only import the things you need instead of all the Third Person Template.
Create a new Blueprint only project based on the Third Person Template.
Right click on Content > ThirPerson > Blueprints
This folder contains BP_ThirdPersonCharacter.
Migrate action will open the Asset Report with all the assets you are going to export:
Select the ones with you need and click on OK.
A Explorer Window will open to select where you want to migrate. You have to select the Content folder of you project and click Select Folder.
After that you will have the mannequin in your project.
Hope it helps.