Normalizing absorbance spectra?

I'm trying to normalize my absorbance spectra (absorbance vs. wavelength) and I am having trouble normalizing the peaks. I've been told many different ways of doing this, but I'm still getting confused. Some of the points on my spectra fall below zero, thus giving me negative absorbances (which are impossible).

To correct for this, my mentor and others in my lab have said something along the lines of this:

(When: abs = Y and wavelength = X)

Find an absorbance value within the spectrum that is closest to 0, then add or subtract that value from every other X value in the spectrum.

They've also said to just subtract the baseline from each spectrum.

This confuses me because I've tried both of these methods and some of my values are still giving negative absorbances.

Does anyone happen to know what they mean by this procedure? Please let me know if I'm missing something or getting something wrong.

Also, please focus on just this method (i.e. the subtraction rather than setting the maximum value to 1 and doing division --I've read up on this already)

Thank you in advance.