A time signature is usually represented by two stacked numbers on a staff, and establishes certain bar settings such as the number of beats contained by a bar and the note value of these beats (number which expresses in how many parts a whole note has to be divided for finding a beat's duration). There are many common time signatures, which include 44, 24, 34, 68, 98, 78. The type of a time signature can vary by many factors such as the number of accents in a bar, the equality of accents, or the general constitution idea for the time signature type. There are simple (like 24 or 34), compound (68, 128), asymmetric compound (78,54), alternative or mixed meters (meters varying from bar to bar, either alternatively or randomly), as well as additive meters (such as 3+24, which are simply compound meters whose accents are defined from the time signature).
The time signature edit dialog Edit
Using the time signature tool (on Clef and signature tools palette), a click anywhere on a staff (except for a text staff) will bring the time signature edit dialog.
At the top of the dialog window, there is a preview area, which shows the appearance of the time signature, as it will look like when inserted on the score. The preview area also features a clef and a key signature, which are drawn in grey or in black, depending on their visibility and presence in the bar specified to contain the new time signature.
An option to show or hide the time signature (which, if hidden, will be shaded in a gray color inside the preview area) also has the sub-option of showing or hiding the time signature all staves. Also, the common time (44) and alla breve (22) meters can be abbreviated as and by the means of "Abbreviate 4/4 & 2/2 time signature".
Below these, there are the actual meter parameters. The "actual" and "displayed" fields are separate, in case you want to display a time signature which in fact is something else. This is very useful in case of anacrusis or other similar situations. For additive meters, an additional field has been provided.
The next area is dedicated to beaming. In meters like 54, this is extremely significant, as it marks the way the bar is split, and therefore where accents will be placed. Click on the scissors to bind or unbind an automatic beam. With "Always beam tuplets" enabled, tuplets will be beamed, no matter if they are crossing a beat.
In the end, the color of the time signature can be set.