What you're looking to do is to create a Hotspot so find that in your settings and follow the instructions to set one up. Hotspots are vulnerable to attack in a crowded situation - outside a cafe for example - so choose a very strong password and only allow devices to share your connection. Also be ware that your mnobile data costs will spike if you allow a PC or laptop into your private network because they can rampy up larger amounts of bandwidth just by opening a browser.