I have 2 bar charts I don't know how to combine them to make a cycle group.
In the dimension tab of your chart, near the bottom under your table list, click 'edit group's
create a new group and select the dimensions for the group, my best guess is %Month and &year
select either cyclic or drill down
A similar process can be done for your expressions too. By creating 2 expressions, putting them next to each other and clicking 'group', you can cycle through expressions as well.
So, you can have a Sum(Sales) by month, by year, or sum(salary) by the same dimensions.