There are three steps to remember when you want to connect your laptop with projector.
1. Connect HDMI cable to projector and to your laptop
2.In projector you can select the hdmi port by pressing source key on your projector. In case your projector has auto source option, select that, so in future you don't have to do this process again.
2.As default laptops are meant to display on laptop screen, to change the display to projector you will be having monitor symbol in function keys on the top of the laptop keyboard press it [ this function key differs in laptop to laptop, but it will be either F3 or F5] [ note some laptops have dual screen support, to do this - right click on your screen, it will give display properties-select it, there you will have dual screen support option- select]