First we need to address the terminology:
Tecnhnically "advertise" means using Facebook Ads, but you can advertise something on Fb or Ig with a post and getting organic engagement.
Effectively doing the second (organic engagement), is every day harder due to the content overload on social media and the reduction of users attention. Every year we have less seconds of attention available to conquer our ideal target.
Some of the advices you got from the others will help: you need to create content that is relevant for your audience, engage, educate, inspire.
Videos work better than anything now and of course a decent copywriting helps too.
Using the actual advertising tools, which means using a budget and trying to reach a bigger audience, can't be explained in a few tips, there aren't quick tips to apply especially if you never did.
Focus on who you want to see your ad and on what they see, so once use as advertising medium a content that is relevant, engaging and inspiring, choose the target carefully, be clear, honest and transparent and...read Facebook rules: advertised posts have a lot of strict rules to respect in terms of topics, language..
for example on your FB or IG profile you can talk about weed freely but you can't advertise anything related to it.