Insert the Form into a Page
Go to the page you wish to insert the form into and click the edit button to bring up the WYSIWYG editor.
Enter the code: {jform=1} where you would like the form to be.
Where 1 is the id of your form (which you can find by going to components>forms and in the ID column of the form you want).
Link to a Form
If you are not already, go to the backend control panel and go to components>forms. Find the form you wish to link to and copy the url that is in the url column for that particular form you wish to use.
Then open up the editor for the page you wish to insert the link to and highlight the text you wish to be the link text. (ie. click here to fill out our online form). Then click the 'insert link' icon and paste that link you copied into the url field.