You can define masks for the individual bits (they may already be defined for you in an appropriate header file), e.g.
#define RI1 0x01 // RI1 = bit 0
#define TI1 0x02 // TI1 = bit 1
#define RB81 0x04 // RB81 = bit 2
...
and then to test RI1:
if (SC1CON & RI1)
...
To set RI1:
SCICON |= RI1;
To clear RI1:
SCICON &= ~RI1;