There are 4 different ways to develop software using the yocto project:

Extensible SDK

The extensible SDK provides the yocto workflow without the need to first set up a full yocto build environment Setup and Building, as this is already included in the eSDK.

The eSDK must be installed in the same way as the SDK and before using it, you must run its source script. After this you rely on devtool.

The official yocto documentation can be found here

Build Natively

This is the simplest but also least useful way to build packages for yocto. By default, there is no toolchain installed in the image.

To add the toolchain to an image, append tools-sdk to CORE_IMAGE_INSTALL.

dunfell and earlier:

CORE_IMAGE_INSTALL_append  = " tools-sdk"

honister and later (namely kirkstone):

CORE_IMAGE_INSTALL:append  = " tools-sdk"

Note that this will significantly increase image size and build time.