How to delete a HDI partition on El Capitan

[GGERARD]

Hello,
I know that the issue has already been addressed but I do not find the solution and I'm on Beta El Capitan.
I have a DDI 1TB partitioned into 2 equal parts.
On one, I 've Yosemite (I do not like it) and on the other, El Capitan that works wonders.
For safety, in addition to my Time Capsule, I saved on a partitioned External Hard Disk the Macintosh HD (Yosemite) and Macintosh HD2 (El Capitan).
I wish to delete the partition and recover Yosemite 500GB for El Capitan on the Internal Hard Disk.
can you help me to delete the partition just to have one?
Thank you for your help
GGERARD

 

[Evren Carven]

Start your Mac into El Capitan. Go to 'Disk Utility' -> Select the internal hard disk for Yosemite and El Capitan -> Partition -> Choose the Yosemite partition to delete. Please backup your important data before do any deletion operation.

 

[GGERARD]

Thanks Evren Carven,
not so easy because you can't delete Macintosh HD!
I've called the Hot Line Apple, the Lady I had on tel. said me that it is not possible to delete Macintosh HD, Only Macintosh HD2 ( the second I've created ) was possible. And it was a new problem for me, because I've installed El Capitan on Macintosh HD2!!
I had to delete Macintosh HD2, resize Macintosh HD using the Recovery HD ( command + R ) and reinstall El Capitan on my new Macintosh HD from my CCC Clone.
Then, also reinstalling all my Apps and documents on this new Macintosh HD.
All is now perfect, I've only El Capitan on an alone HDI partition whose name is Macintosh HD ( as at the beginning ) and all work perfectly well.
GGERARD