A NAND gate can have two or more inputs (e.g, a 4-input NAND gate). Type the desired number of inputs in the "Inputs" field, or use the pop-up keypad to click in the number.
By default a single gate is created, with each input being a single wire. Multiple NAND gates, with each 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 NAND gates, with the inputs of each gate being the corresponding bit position from each wire in the input bundles. For example, specifying two gates (bits) will produce the equivalent of two gates (one symbol), with the inputs of one of the gates being from bit position 0 of the input wire bundles and the inputs of the other gate being from bit position 1 of the input wire bundles.
A NAND gate can point in any of four directions: up, down, left or right. Pointing right (the default) means that the output of the gate is to the right of the inputs. Select the orientation of the gate you are creating by clicking on the appropriately labelled button.
The characteristics of a new gate can be copied from the previously created gate of the same type by clicking on Repeat Previous NAND Gate.
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.