Many blocks have been designed to be fullwidth or wide width which are two options that place the content of the block outside of the normal content width of your page. Support for these options depends on the theme you are using. If you do not see these options in core blocks like the Image, Cover or columns block then it means your theme is not built with Gutenberg support. In that situation I suggest contacting the theme author or looking for a new theme.
How to set a block to fullwidth
When a block is selected there will be a toolbar right above the block where you can see block specific options/settings. Near the left, you should see an align option. Click on that to open the options and then select fullwidth.