Once the yeast mix is bubbling/foaming, add the yogurt and oil, give it a little mix and then add to the dry ingredients and combine with a spoon to start with. The mix should be fairly sticky.
Add a little flour to the bowl and your hands to prevent sticking, then gently knead for a minute. If it's sticking to your hands too much, add a bit more flour (but only add enough to be able to successfully knead it without it sticking to you too much to work it).
Lightly grease the large bowl you used to make the mix with some oil, then add the dough, cover with a damp tea-towel and leave to rise in a warm place for 1-2 hours (2-4 hours if you're not using fast action yeast). You can get away with just the lower amount of time if you're in a rush.