Question: how to pxe boot sccm?
Answer: Open the tab PXE.
Select Enable PXE Support for clients. ... 
Ok, now we have activated PXE, and WDS will automatically installing on your SCCM server. ... 
Click on the tab Data Source.
Select Deploy this boot image from the PXE-enabled distribution point and click on Apply.
If asked for an update, click Yes.