It depends where you want your ads appears. If you want it to appear in the post or page content manually, in the editing screen just switch to HTML mode (it’s labeled as Text mode) and paste the code there. Also you can paste the code into Text Widget (Appearance > Widgets) so it will appear in the sidebar.
Or use this kind of plugin
https://ww.wp.xz.cn/plugins/ad-inserter/
thank you very much for your prompt response. Chatrudee
Hi there, also, can we have the comment box at some pages too/how? thanks
WP gives users full control over the comment.
This is global setting page for comments
https://codex.ww.wp.xz.cn/Settings_Discussion_Screen
Also we can control the comment in post/page individually
https://codex.ww.wp.xz.cn/Comments_in_WordPress#Enabling_Comments_on_Your_Site
If you don’t see comments available at “Page”, this means that your theme only have comments on “Post”. This is good actually because most of the time we don’t need comment on “Page”, a lot of people want it removed.