If you have android download foxfi from playstore as it tricks your provider so that you dont get charged a bill for using hotspot. Another alternative for android is to root it and flash up some after market love and use the built in hotspot. If you have an iPhone or anything other than android, my best advice is to go get an android haha im sort of biased though
That's a little convoluted. The only way to have your phone act as an adapter is to have it set up as a hotspot. It would be easier to purchase a cheap USB Wi-Fi receiver for the laptop, if that's feasible for you.
It's a pretty simple solution, just like what Prostar said above. Setting up your phone like a HotSpot is the best solution (there should be a section that let's you enable your hotspot and it should produce a network name and a password). I used to do this all the time when I was in hotels and it's very viable, depending on your network provider.
If you let us know what phone you have, we could walk you through it step by step!