I have a Kustom KBA100 amp (http://www.romandrums.com/store/Kustom-KBA-100-Bass-Amp/index.htm) with two inputs: CD/TAPE and GUITAR. I'm a total noob to this world of amps. I know I should be able to safely pass a mic through this bass amp, but my question is how? The GUITAR input is taken up by my bass (obviously) so that leaves my CD/TAPE input for the mic, but the amp has no volume controls or amplification ability on the CD/TAPE input... so, how to do I make this work as cheaply as possible?
Guys at Guitar Center said I could either pass the mic through a preamp and then to the CD/TAPE input, or use a mixer (like a 2-channel mixer) instead of the preamp and do the same thing. Will this provide enough volume to hear vocals over the bass?
yep the idea of using a cheap little mixer is sound, the idea of using a bass amp for vocals less good. The frequency range of vocals is so much higher than the bass and the bass amp won't be designed to do that job. It may be good enough or may not.

I've written a bit of a guide to this sort of thing for UG https://www.ultimate-guitar.com/forum/showthread.php?t=1591207