Digital marketing is best way of promoting a website or business. in this all online marketing technique used like SMO. SEO,PPC, Video promotion and Email marketing

Search Engine Optimisation will be your best bet. Google it, there's HEAPS of tools out there for you.

Firstly setup your website properly,
check if all urls are working,
make sure to write titles and descriptions for all individual pages,
add your business website to business listing,
start submitting to search engines,
directories,
participate in forums, question and answer sites,
make your presence in social media,
create profiles
above all create quality content,
make a blog page and promote your business there, it should give you good results.

6.What are the best resources for this kind of promotion - where to post them?
7. Do you have some examples of the communities of the kind?

Thank you.

Hire someone who is best in Digital Marketing. Or if you want to do it yourself then you can Learn about Basic SEO and SMO. For basic SEO activities you can check "Moz Blog" and for SMO you can check "Neil Patel Blog". You also got content marketing help from "Neil Patel"

marketing
 

Seo, press release, article marketing, managing social media.

Do SEO and SMO on your website.

You can promote your website with the help of following ways:

You can take the help of Paid Advertisement
Join the Communities on relevant forums
Videos are in the trend, share on all the social media channels
You can Bookmark your website
You can do Business Listing
Create attractive social media posts
Content is the king, so create backlinks through good content

keep posting regularly

make sure your site is SEO optimized

Promote Your Article Across a “Wider” Variety of Platforms, such as Quora, Tumblr.
Create a Slide Share Overview of Your Post.
Pin Your Post to a pInterest Group Board.
Link To Influential Blogs So They Link Back.
Make your content Easy To Share.

You can promote through Facebook, Twitter, Facebook ads, Google Ads

you can promote with Google Adwords, Facebook campaign also use paid website who promote the website only. also share with social networking site like facebook, twitter, Instagram, google+ etc. there can be get more audience to visit the website.

Note: First make sure that your website running proper at any platform like desktop, tablet, mobile smartphone..!