Statement

For constants $a,b$ and integrands $Y^{(1)},Y^{(2)}$,

$$ \int_0^t (aY_s^{(1)}+bY_s^{(2)}),dB_s

a\int_0^t Y_s^{(1)},dB_s + b\int_0^t Y_s^{(2)},dB_s. $$

Meaning

The Ito integral is linear in the integrand, just like ordinary integration.