to make my apk's i use Intel xdk.
So first download Intel xdk and make a new project. it usually creates the folder on the desktop(not sure but mine are always on the desktop).So let's say you create a project called construct in the XDK, it makes a folder called Construct 2 on the desktop .
now export your construct 2 game using the option called android(the first one in mobile) and and export it to the folder where your intel xdk project is which in this case is construct 2 on the desktop.
You may be asked to replace files, say ok.
now go to the develop tab in xdk and refresh the file tree(by right clicking and choosing the last option on the left side of the xdk screen). You must see the exported files shown there. then go to the emulate tab, choose device and test it . if everything is fine, go to the build tab (you might have to login to build so make an account if u dont have one) and choose crosswalk for android which is the 4th option. it will ask you to fill in details and assets(u know, like the icon and splash screen and name and stuff). it will take some time to build and would get a screen where you can download the apk file or send the download link to your mail.
Glad to be of any help