Is there any method for using Android applications on a computer, because I found this tutorial but my laptop just has 1 GB of RAM and works very hard. I want to use WeChat on my PC because I like it very much.
You need either Bluestacks or Youwave. I think Bluestacks can not be installed on your PC because of less RAM (minimum of 2gb recommended). So Youwave is your only option. It is easy to install and use.
You might wish to take a look at my list of emulators – the ones you will need are to be found at the end of the page. I personally use android-x86 in VirtualBox, which works fine – but you might have different demands. For just one app any of them might be a little "overkill" – and you might find it easier to install a VNC-Server on your Android device to access the app via that. Which would have the advantage of doing even more on your device remotely ;)
Bluestacks is the best so far, but I don't think it will run on a PC with 1GB of RAM.
As for YouWave, you need a few bucks to use it, so it's not a free tool. But there is another tool that might work well on your PC, it's called Andy and it's the best free alternative to Bluestacks so far.