All elements of the search filter must be contained within the SearchSolrFilter Block. This block has a filter setting, that is used to determine what the search filter can find.
Example to find all pages, blog posts, and news posts, set the filter to:
Relation: No Relation
Type: bldpage news blog
And leave the rest of the filter settings alone. You can also toggle the Show on Search option, this determines what happens when you open the page before clicking the search button, do you want to show something. Generally for search pages, you want this option de-activated, however if you are adding a filter to a category, or news, or similar page, then you want this setting active.
Within the search filter block you need a search results block to display the results. This results block has settings for the output of each result, you can use grid, or list mode Change the padding, and the layout slice that is used to render the result items. You should add a message for no results found inside the Search Results block.
Now you need to add one or more fields to search your site and a search button. At a minimun this woudl be a Search Keywords block and a Search Apply Button.