adding node with latitude, longitude

In iD, you can open the location panel Command-Shift-L (mac) or Control-Shift-L (windows) to see the exact coordinates of the mouse pointer, then place the point exactly where you want it.

When I want to do this, I use the Level0 editor (http://level0.osmz.ru/). Documentation at https://wiki.openstreetmap.org/wiki/Level0. Basically, you just type (for example):

node: 12.345, 6.789

give it a changeset comment, click Upload to OSM, and it will create a node at that location, which you can then edit in iD. Or you can supply all the tags in Level0, e.g.

node: 12.345, 6.789
name=My Node
amenity=bar

Do you have a list of the points, or do you already have a KML or GPS file? GPX files can be added into the ID editor screen on your browser, so that the points will show up at the exact coordinates.

If you have a file in KML (Google Earth) format, you can convert it to GPX at gpx2kml.com, and then downlaod the GPX file.

If you just have a list of coordinates, you can make a GPX file at www.gcgpx.cz

Once you have the GPS or GPX file downloaded, just drag the file into the map in your ID editor browser window. It should show up as bright purple lines and points with labels. Now you can zoom in to each point and get things exactly right.