Wrap text with lines

click on the text box to select

Inspector > Format > Style; in the Border dropdown menu select: line

click the colour circle to change colour

click the border style dropdown, select the required style

You mean outline text: unfortunately Keynote does not have the full settings to do this properly,

top is outline text and bottom has a shadow applied:

the settings for outline are shown here:

if you have other applications that use text; e.g. MS Office, Photoshop you could import an imagage file into Keynote:

this is what Word can do, the outline setting is arrowed: