How do I change from portrait to landscape format to write a document?

I have no other details. Question seems clear to me. Thankyou

Use page styles. Page formatting details like page size, margins, orientation, headers and footers are controlled by page styles.

See Tutorial on Page styles and headers/footers for how to work with page styles. For this case: insert two manual page breaks (Insert - Manual break - Page), one at the bottom of the page before the page with different orientation and one at its bottom, and change page style to Landscape for the first and to whatever your default page style is for the second.

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too complex

I got the answer by asking the www. Go to Format on the upper tool bar, then Page on the dropdown menu, then Paper, then Format Select.

thank you - a simple answer!!!