In 1st gear

Hydraulic pressure is applied to the 1st clutch, then the 1st clutch engages the secondary shaft 1st gear with the secondary shaft.
Mainshaft rotation is transmitted to the mainshaft 4th gear splined with the mainshaft
The mainshaft 4th gear drives the secondary shaft idler gear splined with the secondary shaft and the secondary shaft via the idler gear shaft idler gear.
The secondary shaft and the secondary shaft 1st gear engaged by the 1st clutch, and the secondary shaft 1st gear drives the countershaft 1st gear.
The countershaft 1st gear drives the park gear splined with the countershaft via the one-way clutch.
Power is transmitted from the countershaft to the final drive gear, which in turn drives the final driven gear and the transfer drive gear.
As the final driven gear turns the differential assembly, power is transmitted through the transfer drive gear to the transfer output shaft that drives the transfer hypoid drive gear/shaft and the transfer output shaft (hypoid gear).

Fig 1: D Position And S Position With Automatic Shift Mode - 1st Gear
Courtesy of AMERICAN HONDA MOTOR CO., INC.