If you are not a designer, it is recommended to tidy up. Just be neat and clean, without pursuing a strong sense of design. Specific practices are as follows:

Information arrangement

The information is well organized and the level is clear. Main title, subtitle, text, additional content, etc.

Theme text amplification

Then enlarge the theme text as the main body to attract people. You can download a beautiful font on the internet to avoid the embarrassment of not designing it.

Text arrangement

Put the text in the main position, and then put other additional contents, such as time, place and organization, in the corner, so that the poster looks cleaner.

Reference case

I found two cases for you online. You can combine them for reference.