There are 3 ways you can find a post.
From your homepage, click on the home tab, and filter by 'posts.' You will be able to scroll through the posts until you find what you're looking for.
Another way is if you know the author of a post. If you do, type their name in the search box of your homepage. Their name will come up and you will hit enter.
You will be taken to their profile. Scroll down a bit and you'll see find their activities section. Within the activities section, you will see their post. Click on it and it'll take you right to it.
The third way is from your homepage. If you recall a keyword of the post, type the word in the search bar, and the results will appear. Click on 'see more results.'
You will be taken to a search page where you'll see several options of 'all, people, referrals, and posts' on the left side. Clicking on an option will get you specific results.
For example, if I'm looking for Jenni Brennan's post regarding 'parking lots,' I will type that keyword (parking lots) in the search bar. When I did, the post appeared. Clicking on it took me right to it.