For Android 6.0/6.0.1 custom ROMs, you will need to use Android 6.0 Marshmallow compatible Gapps. Without this, you will not have Play Store on the phone.
The following Gapps is very simple and minimal and includes the Play Store. If you need other Google apps, you can use Play Store to install them.
These Gapps do not come with a camera app, you can use Google Camera app on the Play Store.
These Gapps will work on CM13 ROMs and any other Android 6.0 ROMs such as Resurrection Remix ROM, CrDroid ROM, AICP ROM, AOKP ROM, Dirty Unicorns ROM, and much more. Gapps are really ONLY for AOSP ROMS(What is AOSP?)
Credits – Euroskank
How to Install Marshmallow Gapps
Installation is easy, follow these steps:
Step 1. Reboot into TWRP or CWM.
Step 2. Do a factory reset (if installing a new custom Marshmallow ROM).
Step 3. Install ROM.
Step 4. Install Marshmallow Gapps
Step 5. Reboot.
That’s it! If you have trouble, take a look at How to Install Marshmallow ROM using TWRP!
Note: Some ROMs DO NOT REQUIRE Gapps such as TouchWiz-based custom ROMs for Samsung Galaxy phones or LG custom ROMs based on LG firmware. If in doubt, you can always install your custom ROM FIRST, then after booting if you don’t see Play Store, you can go ahead and flash Gapps after using TWRP separately.
Q: My phone is getting errors after flashing both ROM and Gapps!
A: Try doing a factory reset in TWRP recovery and rebot without reflashing Gapps. Sometimes that will get rid of all errors, so flash ROM, Gapps, THEN do a factory reset.