NB: pls note this topic is just for educational purpose only. Developers are trying thr best please buy them some bear
This topic might have bn treated here, I don't know but for those who might still want to know how this is done just take a moment and go through the process.....(on android though)
The first method is for both Rooted and Non rooted phones, while the second method which I consider the best is just for Rooted users only... straight to the point...
Method 1:
1.Download Parallel space from play store or search on google.
2. Install parallel space.... open it.... u should see a kind icon at the bottom click on it.... about six other apps would pop up.... after the last app u would see a MORE symbol click it.... all your apps in ur phone would load up.... look for the app you would love to clone and click it this would take some seconds and ur good to go.
NB: using this method you can only clone 1 app per phone.(just two facebook account or two whatsapp account ...u can't have 3 whatsapp or 3 facebook)

Method 2.
Which I consider the best to me... u can run ten whatsapp acount on ur phone, ten facebook account and so on.. only for rooted users
1. open google and search for titanium backup patched
2. Once u see any suitable version download and install....
3. Open the titanium backup patched version
4. In the overview section (u can know the section u are by looking at the top of the app, there are three sections overview,backup/restore,schedule I think)
5.next thing to do is create a profile (the number of profile u create determines the number of accounts of the same app u can get)
6. U would see this at the bottom of overview section
7. Create as many as u like.
8. Next... click the backup and restore section
9. Locate the app u would love to clone.
10. Click and hold
11. A dropdown would pop up....you would see enable multiple account for this app...
12. click enable...
13. Once dat is done... go back to overview...Then choose a profile... close titanium then launch ur app u would be ask to sign in into the app... once that is done, close the app go back to titanium choose another profile close titanium then launch the app u would be asked to input ur details use another details... this repeats itself until all ur accounts is filled up.. then any account u want to use just goto titanium select the profile nd lauch the app that's all...... For those who want to be running two whatsapp and be receiving msg instantaneously u can try Gbwhatsapp