You have a couple of options for adding blocks of text to your form:
Add text to the form description: This is shown just below the form's title.
Add text to field descriptions: This can be shown above or below the field, or as a tooltip. This can also be combined with the section header functionality, to add a description to a section of the form, or a page on the form when using multi-page mode.
Add a formula field or read only text field to your form containing the text you want to display. Formula fields can also be displayed using HTML code for further flexibility. This option only works when editing existing records or when using Save & Continue mode.
Add text to the form footer: This is shown above the submit button.