By default a single tri-state gate is created, with each input being a single wire. Multiple tri-state gates, with the input being a bundle of wires, can also be specified by typing or using the keypad to enter the desired number of gates in the "Gates (bits)" field. The resulting single gate symbol will then be a shorthand for multiple tri-state gates, with the input of each gate being the corresponding bit position from each wire in the input bundle. For example, specifying two gates (bits) will produce the equivalent of two gates (one symbol), with the input of one of the gates being from bit position 0 of the input wire bundle and the input of the other gate being from bit position 1 of the input wire bundle.
To finish the dialog and place the newly created gate, click on the OK button. Then move the mouse to position the gate where you want it in the circuit and left click to fix it in that position (it can be moved later, so don't have to be in exactly the right spot).
If you change your mind and decide you don't want a gate of the type you are currently creating, click on the Cancel button in the dialog. If you have already clicked on the OK button but have not yet fixed the place of the new gate, you can still cancel the gate by right clicking the mouse.