Okay, to answer my own question...
It appears that the typical way to go is to have exact change ($1 each way) to deposit into the "farebox" each time you hop on.
Day passes ($2) and 3 day ($9) passes also "may be purchased on-board from the trolley operator". Whatever that is (person? machine?) It's also unclear if 3 day passes are available, because their website says they "will not be sold at this time due to COVID-19". Note: it also doesn't make sense to buy a 3 day pass when it's $3 cheaper to buy 3x single day passes.