Just started learning Japanese and have question with the following sentence.
Do I have to use の in this situation? Can I just say わたしはえをみるがすきです without the の？
You seem to be a native English speaker, so try thinking about it this way.
The sentence could be roughly translated as follows.
I like looking at drawings.
However, could you say the following?
I like look at drawings.
No. That is not valid English because you can only like a noun. "looking" is a noun that represents an action.
Similarly, えをみる is a verb. You cannot like a verb, so you have to nominalize it (convert it to a noun). That is what the の is doing, and that is why it is necessary.