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You'll need examples of your product, so if you haven't, you'll need to put together a portfolio of your finest works, one that covers a variety of examples.
Once you have your portfolio, you can contact companies who you think might be interested in your style of illustrations and see if you can get them to accept a copy of your portfolio. The more companies you can get to accept your portfolio, the better the chances that one of them will like your style and designs and may decide to hire you.
In addition to actively marketing your portfolio, you can post it online in any of a number of online art galleries. The good ones require a small fee, but those sites are regularly browsed by potential clients who may contact you for employment or contract work. At the very least, you'll be able to display your work to the public, possibly sell some to consumers, and develop a fan base. Social media is also a good publicity outlet, but make sure you use low resolution images and watermark them to prevent theft.
There's a lot more to marketing artwork, but this will point you in the right direction.
Most Helpful Girl