One way:
Use the checkbox from the Forms toolbar (activate by going to
View|Toolbars..., put a check next to Forms). Click on the checkbox icon (it
should depress, and the pointer should be replace by "+") then mouse to
where you'd like the checkbox, left click and drag to the right and down to
set the size.
You can tie this into a cell, which will show TRUE or FALSE, depending on
whether there is a check in the check box. You'd also be able to check and
uncheck by changing the cell to TRUE or FALSE.
Need more info?
Post back with a specific question.
tim