tiles server issue

i got some troubles with Configuring OSM Bright. it the switch2osm web site they said i need to use nano and "Find the lines with URLs pointing to shapefiles (ending .zip) and replace each one with these appropriate pairs of lines"

what does it mean, how do i use the nano , and can i looking for shapefiles.. ? can someone explain me how i do this part .

Configuring OSM Bright The OSM Bright stylesheet now needs to be adjusted to include the location of our data files. Edit the file osm-bright/osm-bright.osm2pgsql.mml in your favourite text editor, for example:

nano osm-bright/osm-bright.osm2pgsql.mml

Find the lines with URLs pointing to shapefiles (ending .zip) and replace each one with these appropriate  pairs of lines: "file": "/usr/local/share/maps/style/osm-bright-master/shp/land-polygons-split-3857/land_polygons.shp", "type": "shape"

"file": "/usr/local/share/maps/style/osm-bright-master/shp/simplified-land-polygons-complete-3857/simplified_land_polygons.shp", "type": "shape",

"file": "/usr/local/share/maps/style/osm-bright-master/shp/ne_10m_populated_places_simple/ne_10m_populated_places_simple.shp", "type": "shape"

Note that we are also adding “type”: “shape” to each one. (If you’re using nano, to save, now press ctrl-X and Y.) Finally, in the section dealing with “ne_places”, replace the “srs” and “srs-name” lines with this one line:

"srs": "+proj=longlat +ellps=WGS84
+datum=WGS84 +no_defs"