Good Night Liliana, it is very easy to connect the ballast that you indicate in your request .... Considering that you are learning to make electrical connections for lighting, first I will give you some practical theoretical basis on fluorescent lamps ...
By basically observing the connection diagram indicated by your Ballast, you can clearly identify that the ballast is for two fluorescent tubes that are called in the image (LAMP). You can also see that the ballast has 7 connection points where a cable can be connected. For now, skip the colors and cable lengths. Those colors are raised like this, for electrical installers already experienced. Your connection at this time can be made point to point so you do not get confused and can do a good job without mistakes.

Before making your connections, let's talk about fluorescent tubes ... In theory your lamp has two fluorescent tubes, possibly 32 watts, 40 watts; Most Fluorescent tubes have two contacts
at each end and the base where the fluorescent tubes are inserted it also has two contacts or pair of wires.

Now, with the permission of Mr. Montenegro, Taking his previous image to improve it a little in view of Liliana, you can easily make the connections as indicated there and from this I clarify some circuit concepts:
one-. The connections at each end of the fluorescent tube do not matter if they are reversed, that is, for example, specifically in your case: If you look at the first fluorescent tube it has on the left side the connection 1 and 2 that come from the ballast. These two cables can be connected, one in each Pin regardless of the Pin you select for each of the cables.
2-. Specify the question you asked about cable number 4 of the Ballast, this usually confuses many because they do not know the concept of NODE ... Translated into Spanish, cable number 4 of the ballast is connected at the same time in a Pin of the lamp 1 and a pin of lamp 2.
Well Liliana, if you have not solved the problem until now, good luck, Regards ...