You create groups (or team, whatever you call it) with UTeam. Then you create users with ULX users file (addons/ulib/data/ULib/users.txt) by adding them in their respective groups you just created with UTeam.
But i agree..it's a pity that it's not easier to add people.
Here is how i would like to have ulx team, will be much easier.
"Team1_name_Here"
{
"walkspeed" "200"
"sprintspeed" "500"
"others options" "etc"
"users"
{
steamid_0_0_123456
steamid_0_1_654321
}
}