For stars, use "Selected Stars" (AP 3270/NP 303) Epoch 2010.0, and calculate Local Hour Angle of Aries at nautical twilight (time in GMT for nautical twilight taken from the Nautical Almanac) for your Assumed Position thus:-
LHA Aries = GHA Aries (for the Hour GMT, from Nautical Almanac) + Increment (Minutes, again from Nautical almanac) + Longitude East (OR - Longitude if you are West or Prime Meridian). i.e.
LHA Aries = GHA Aries
+Inc
+ Longitude East OR
- Longitude West
If it's less than 360 degrees then add 360. If it's greater than 360, subtract 360 degrees. Now you have the Local Hour Angle of Aries.
Then, find the page for your your Latitude (in whole degrees) in "Selected Stars" and look down the column on the extreme left marked LHA Aries until you get to your calculated LHA Aries. In that row you will find the tabulated Altitudes and Azimuths (True) for seven selected navigational stars at various azimuths. You don't need to know them by sight, the sextant will find them for you using the following procedure.
To get a star shot (at dawn or dusk), calculate the local time of Nautical Twilight (for dawn or dusk), and at that time (or preferably a few minutes earlier,) pre-set your sextant to the altitude of the star you wish to shoot, then go to your compass (gyro or magnetic, in which case you will have to correct for magnetic variation), line your sextant up on the bearing (i.e. azimuth) and look in your eyepiece. Somewhere in the field you should see a small bright spot...that's the star! You might not be able to see it with your naked eye, but the sextant star-telescope will help. Using the adjusting-drum, bring the star to the horizon, rock the sextant to make sure the star just grazes the horizon, and note the time of the shot to the nearest second. Accurate timing is vital!
Now, perform your Marc St Hilaire sight-reduction using the values of time, Sidereal Hour Angle and Declination for the star for the time of your shot obtained from the Nautical Almanac,and compare it against the observed altitude (corrected for Dip or height-of-eye, sextant Index-Error and refraction) for your assumed position. There will be an error of some number of minutes of angle (i.e. nautical miles distance).
The difference is your error in position, which you will plot on a plotting-sheet. Remember the useful acronym "Coast Guard Academy" - Computed Greater Away. In other words, if your calculated altitude is greater than your corrected observed altitude, then you are further away from the star along the azimuth. Your Assumed Position is the origin of the azimuth-line on which you plot your line of position (LOP). Plot the position-line thus obtained from the comparison of calculated versus observed.
Repeat for some other stars, and try to get shots of stars which give a good angle of "cut". Work from the East to the West because in the evening you lose the eastern horizon first, and in the morning you get the eastern horizon first.
When several such stars are plotted they will not intersect in one point but will define a smallish area called a "cocked hat". You are somewhere inside that "cocked hat". That's your fix by stars.
I still practice this, but it's been a long time since I stood on the bridge of a ship.