I understand how much it can be disheartening in the first weeks, but hold on.
For now, you have to go forward and grit your teeth if necessary.
Your objectives should be:
- go through an intership, building relationships that will look good on your CV;
- Actually learning skills and advancing your education in the field.
Some advice on the problems you mentioned:
I have just been making updates on a WordPress website and doing graphic design.
Did you agree on an "area of interest" for the internship, or they are free to let you work on anything?
In any case, you're free to ask - politely - for more work or work in a different field. E.g., if the company as some interesting IT project, you may ask to have a look at it.
Remember, though, that they probably gave you simple tasks since they don't know - yet - if they can "trust" you with anything more. Also - sadly - interns are often seen as "cheap, easy, low-level workforce" so they could be trying to give you the menial tasks nobody wants to take care of.
My mentor seems almost clueless, whenever I ask him a question he usually redirects me to another person
This is not bad, per se.
Are the people he redirects you too knowledgeable? Are they willing to teach you (or at least answer some basic question once in a while)? I'm not saying they should spoon-feed you. The point is: if you can learn from them, you should.
They haven't told me how to clock-in and clock-out on the day I started, even if I asked (I realized another intern was doing it).
Ask again. I didn't understand everything on my first day of internship, quite the contrary - I looked at what others were doing with eyes wide open. But there's no shame in going to your mentor and saying "hey, I'm not sure I understood the whole clock-in thing. I've seen that intern Bob is doing it, should I do too?"
At the end of the day you are there to learn how the company works, so don't be afraid of asking even the silliest question.
To sum up:
Let some time pass, see if things go better, and in the meantime shift your focus on how you can solve the problems above.
If after, let's say, a month, nothing improves and you still see no value in keeping with the internship, it's safe to start thinking about other options (like complaining with your mention, resigning, etc.).
Internships should be very formative occasions, but sadly this is rarely the case.