Go to the Home Screen and highlight the game software you want to update.
Then press the + button on the right Joy-Con.
Highlight “Software Update” and select “Match Version With Local Users” option.
Click “Next” on the page followed.
One of the Switch users should select “Create Group” and the other(s) should select “Join Group” and join to the group the other user created.
The user that created the group then must select “Start Communication”. And whoever needs to update their game gets the update from the latter.