Hello Sir,
Yes, It is hard to promote a single page website; “Google gives search ranking boost to regularly updated website.” & A single Page Website is rarely updated because it is just one page.
However below steps are useful to promote single page website:
– Use Appropriate keywords and keyword phrases only to promote your website
– Keywords should be included in meta and title tags as well as page content. It is important to avoid repeating the keywords too many times. Search engine spiders categorize this as over-stuffing of a keywords in web-page.
– A blog is necessary to promote a single page website & fresh content of the articles should be engaging and informative.
– Advertising: PPC or Facebook advertising will help you to promote single page website & caching leads.
I hope this answer helps you!