Field units in XCOM: Chimera Squad are not affiliated with your agents or androids in any way. They are teams that you create on a city map and that bring in certain bonuses once a week.
From the very beginning of the game it is possible to create level 1 field squads for each area in the city. Pay attention to the dissatisfaction scale in the area. To the right of it, at the very end there is an empty square. Click on it and you will see a menu for creating and improving the field squad. There are three types of field units, and all of them can be upgraded to level three. There is also a description of bonuses that the warband provides on the first, second and third levels.
At first you can only create level one warband. Intelligence is spent on this – one of the three major game currencies. To unlock the second and third levels of the field squads, look for appropriate research in the assembly complex.