Hello, if there is a clothing company with the same as mine, can I for example add the word apparel at the end to make it different?

That depends.  If you added the word "apparel" to "McDonalds", consumers are not likely to  confuse your apparel company with McDonald's fast food restaurants.  However, just adding the word "apparel" to "Aeropostale" would not get you off the hook.  By using the term "Aeropostale", even with the additional word "apparel", consumers would still confuse your business with theirs; you would be trading on their goodwill and name recognition, and consumers would think they were buying clothing from the original Aeropostale, not  your new business.  Some more fanciful and less descriptive term might help to prevent confusion.  In other words, "influx apparel" will probably not pass muster if there is another "influx" clothing store, but "influx benini brothers" has a better chance; the first term "apparel" is just descriptive and doesn't distinguish the two marks.  The second one might still not be different enought to avoid confusion, but it has a better chance.