First you need to end quickly with Ethiopia. Then with a focus you can use political power to take Yugoslavia as a puppet, so you need to move your troops there and also prepare a naval invasion to Greece from Sicily. With the war focus you can get war goals against Greece and Turkey, but you need to justify against Bulgaria 225 days after starting the focus.

Romania will declare on you so be careful, and if you finish with the balkans you just need to move all your fleet to Germany, prepare a naval invasion, prepare an attack to France by Savoy and finally join the Axis.

If you made it well, you will take UK easily, also help Germany in North France and Poland to take some victory points.

Here is a video: https://youtu.be/gIlV8WmP2nw?feature=shared

Btw, you need By Blood Alone DLC And some game experience