Create a company account/page for Facebook, Twitter, Instagram, and Youtube. You can add more as you go, but these are the 4 main platforms you want to utilize in the beginning. I would suggest creating supplementary accounts such as Pinterest, Snapchat, and LinkedIn down the road. However, depending on the industry you may want to get all your social media platforms set up.
Once your accounts are live, add your website link and your new logo, which you create from the next step. I suggest putting in a filler logo, just a picture in the general industry you are in until you have a professional logo design. Also, start posting content and following people in your industry ASAP. For example, if you're in the fitness industry, start following people in the fitness world. Look for fitness influencers, start following their followers and post similar content.
Do not wait around to do this, you should post once per day and follow at least 20 people per day on Instagram and Twitter. Use popular hashtags in your industry in posts to get more engagement. Instagram and Twitter direct messages are also a great way to connect with people.