Basically you can use Open every time as it works both for new and existing projects.
The only additional feature of Import is that you can set new project name and location if you wish to and additionaly do some basic config stuff such as Add Framework support (but thiis you can do even if you open project later). My personal preference is to use only Open as Import is rarely necessary for me.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…