How do I assign an input to a channel?

The I/O screens control the input/output assignments,
as explained here:
1 With the SHIFT indicator lit, press the I/O
key.
There are four tabs at the bottom of the
screen. The two leftmost tabs, accessed
through the first two soft keys, control the
inputs to the first sixteen (CH1-16 IN) and second
sixteen (CH17-32 IN) channels, respectively.
2 Press either of the two soft keys described
above. These screens control the selection of
the return block, the input source, and the
choice between input and return for each
channel, as well as the input source for the
DIGITAL IN signals.
Each of the channels from 1 through 24 can be used
either as an input or a return, as described above.
In the screen above, the mic/line inputs are assigned
to the first sixteen channels, which would be an
appropriate setting for the recording phase of a
project. In the screen below, however, tape returns
from TDIF groups 1 and 2 are assigned to these
channels (for mixdown).
Channels 25 through 32 can be used for input only.

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