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.
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!