Each coefficient must be multiplied to its corresponding input value and sum all of them in order to get the prediction output. For example if you data instances input data have this form:

x1,x2,x3...xn

your regression model should get 'n' coefficients, one for each input:

c1,c2,c3...cn

Then, you only need to multiply each coefficient to the corresponding input and sum all:

x1·c1 + x2·c2 + x3·c3 + ... + xn·cn