There is a built-in feature in SolidWorks that will fully define your sketch for you. While this is not always the best tool to use as it can make your dimensions and relations of your sketch complicated. In turn making it hard to change or modify things down the road. It can be a powerful tool if this is not important or for defining splines or other complex geometry.
For this sketch, the straight lines and circles would be easy to make fully defined, but the spline (in orange) could be difficult.
Right click in the sketch field away from your sketch and drop-down menu will appear. There will be an option called "Fully Define Sketch..."
click on this.
A menu will open on the left of the screen and you will have a few options to play around with.
Lets start by just leaving all the settings alone and clicking on the green check.
As you can see, a lot of relations are added as well as dimensions. Our sketch is now fully defined.
But as you can probably tell from this picture, if you needed to change something in the future, this could be a mess.
Also note that all of the dimensions are given from the origin in this example.
Lets go back into the sketch and I have deleted all dimensions and relations.
You can also decide to only use this feature to detention a particular entity that is difficult such as this spline in light blue.
You can also play around with the relations and dimensions options choosing the specific relations you would like to add or where your dimensions are measured from.
Here you can see that only the spline is dimensioned and if the rest of the sketch entities were defines by us earlier our sketch would now be fully defined.