Custom Post

Hello. I’m a newbie in WordPress development and although I have basic knowledge and understanding of PHP and some of WordPress syntax still I can’t seem to figure out how to customize my posts.

I want to have additional content for my Memorandum Posts such as Memo No., Memo From, Memo To and Memo Re. WordPress by default only have Title and Content to fill up.

I tried looking out for tutorials and stuff but it doesn’t seem to work well in my theme.

I need some intervention here. Directing me to the right path will greatly be appreciated. Thanks in advance!