You can build backlinks by following methods: social bookmarking guest blogging blog commenting PR submission article submission directory submission infographics submission
There are various methods of link building but I will tell you the easy one. If you are good at writing then you must have to comment at highly authorized blogs and websites. Which site has higher PA and DA. I think commenting will be the best way to generate quality links. Just focus on quality link building. Do not ever spam.
You can use various platforms to put your website link. Forums Social media accounts Social bookmarks Articles Blogs
In order to get the backlinks for your sites, try out doing submissions on directories, bookmarkinh and forums. Even blog commenting can also help you more for this.