Sims 3 - How to install second Expansion to existing base game+expansion

Actually, I have two questions to ask. Let me break in down for you.

1. I have already downloaded and installed Base Game + Uni Live. In this link, you mentioned that I should download base game and one expansion and must not crack them. I have to apply the ultimate fix to it uncracked. I have done that and my game is already running properly but now, I would like to add another expansion (Seasons). How should I do it? Would it affect my current game?
Can you teach me step by step? Cuz I'm kind of a  

2. Recently, while playing sims 3, the screen would blank off and sometimes even auto shutdown my computer after a blue screen. Can anyone help me with this?
(Sorry if it is inappropriate to post two questions in one thread but I didn't want to spam)

Thank you very much

And with the blue screen, are you on a laptop? If so, it may be overheating, or a piece of hardware that isn't reacting properly to the game (probably graphics card if so).

Yes I am using laptop. Is there anyway to go abiut it?

Sorry I forgot to mention but rhere is a notificatiin before the game starts saying
" It looks like you have installed an unofficial game modification that does not match your current version of the sims 3. We recommend that you either uninstall these game modificatiobs or get updated versions of them. Or you may experience crashes or significant bugs. Do you wish to quit?"

Is this the problem?

So, does that mean I have to constantly look out to see if there is new update patch and ultimate fix?