Bubble sort is named "bubble" because the largest value (or the smallest value, depending on whther you use < or > in your comparison) will float to the top of the list, like a bubble in a tank of water.
Assume you have a list of numbers, a, b, and c. The bubble sort is a variation on a swap - you compare two numbers, if a > b, then swap a & b. Next, compare (the new) b to c. At the end of the first iteration, the largest value will be at the top of the list. Simply start at the bottom of the list, and do it again. You are done when you pass through the list and no swaps take place.
There are several variation on it to enhance processing time - such as:
the first time through, loop n times, where n is the number of items in the list - 1. Next time, loop n-2 times (because you know that the largest value is already at the top, there is no need to compare it and waste the cycles). I will leave you to discover the other variations.