PSpice仿真问题

WARNING): Your design does not contain a Ground (0) net. You may not be able to run analog simulation on this design.?To run analog simulation,?your design must have?at least one?Ground (0) net.?Use at least one PSpice Ground (0) symbol in the design.?Ignore this warning, if this?is a?digital design.
搞不懂啊，画了一个boost威廉希尔官方网站 ，但不能仿真，时间不能设置，运行图标也是灰色的...
求助大神