A lot of potentiometers come with pins fit for a breadboard. If you don't have one, you can solder some solid 22 gauge wire to each of the contacts, and plug that into the breadboard. Trimpots are specially designed for breadboard and PCB use:
on pots that dont fit my bread board i use a small bit of vario board to solder the pot on (or make a small pcb) and solder some header pins on the vario board so they fit the BB job is done robert is your mums brother well that is what dad said
I've modified several components to work on breadboards, including rotary switches, 1/4-inch and 3.5mm phone jacks, banana leads, coax cables, etc. I use those gold-plated square pins that were so popular on 1980s-era computer PCBs since I have such a huge stock of same, some as long as 1 inch or so. They're stiff and perfect for the breadboard. Just make sure you align all the flats of the various pins so they're parallel with each other.