In Edit mode, open the Family Datasheet by clicking on the tab if necessary, and click on the New button towards the bottom of the window.
Before adding a new family, you should first add at least one of the individuals who is to be a family member, using the Individual Datasheet. To add an individual to the family, select the name in the listbox on the right-hand side, if necessary typing a search string in the edit field above to find the name; then click Add as husband, Add as wife, or Add as child as appropriate.
When you have finished entering details of the family, click on the Add button towards the bottom of the window, to save the information within the program. The background colour of the text will change from white to yellow when the information has been saved.
Before leaving View/Edit modes, you should also save the gedcom file to disk, by choosing Save from the File menu, or clicking Save on the toolbar. You will be prompted to do so.
You can add a second marriage or subsequent marriage for any individual in the same way. Each marriage must be entered as a separate family.