It depends on your Liferay version. I am assuming 7.0 or higher.
One way would be to use an Activator. An activator is called when your module is deployed and you can do any kind of initialization steps there. Basically you just need to add a method with the Activate annotation to a component.
@Activate
protected void activate(Map<object, object> properties) {
// Do whatever you need here ....
}
</object,>
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Of course, this is called whenever the component is deployed, so it might not be what you need.
Another option could be the resource importer. But you need a theme or a site template to do that. Also, resource importer is kinda deprecated nowadays and I would avoid using it for 7.3 projects.
https://help.liferay.com/hc/en-us/articles/360017883012-Importing-Resources-with-a-Theme-Starting with 7.1, there is the option to use a site initializer. There's not a lot of documentation, but there are a couple of examples out there, e.g.:
https://github.com/liferay/com-liferay-commerce/tree/7.1.x/commerce-theme-minium/commerce-theme-minium-site-initializer
