Run PowderX. Select "File", "Import Data" and the format corresponding to your data (here Siemens *.uxd):

Ckick, and this will open a window. Search for your file,

select it and open it. The pattern should be drawn :

Click on the "subtract background" button, a box appears which proposes default values :

You may click on "Show" and the estimated background will be drawn. Using the zoom option, you may look at it and decide if you are satisfied (if not, play on the "pickup point" and "repeating time") :

Note that you have to close the zoom window and open it again at each test. Well, you may not be completely happy with this background proposition, then you will have to explore more in depth the PowderX possibilities about background. Let us decide that, for a peak position extraction, this background is OK. So, click on OK and it will be subtracted.

Then you have to click on the "alpha-2 strip button", if your powder pattern needs it :

Change the 49% if you are sure about another value (here 53%) and click on "test", and have a look at much details by the zoom option if you need :

This seems OK (more options are available, this is the standard one), so that click on "Finish" and the alpha-2 component will be removed. Then click on the peak search button and on "show". Markers will appear where peaks have been located :

If you are unhappy with the PowderX propositions, then you may play with the 3 parameters ("Select Points", Derivative Limit" and "Intensity Limit") up to fulfill your desires.

If you are happy, click on "OK". A box appears in which you may change the radiation and Wavelength, if appropriate :

For instance, you may believe that 1.54056 is more correct than 1.540598, that is your choice. Then, click on OK, and a box will be opened and proposes a name (nist1976.txt in this case) for saving the extraction results :

You may change the name or not. That .txt file contains your peak positions :

The complete file is below. Care to not confuse residues of alpha-2 corrections with real peaks :
 

    2Theta     d (A)    Height      Area     FWHM
    25,574   3,48029    5993,5   58566,4    0,1000          
    35,139   2,55179   18874,0  145082,7    0,0900          
    35,303   2,54026     374,2    3248,8    0,0900          
    37,767   2,38003    2469,4   20254,8    0,0900          
    41,666   2,16587     576,2    4915,4    0,0900          
    43,346   2,08573    8803,4   74545,1    0,0900          
    52,538   1,74040    3979,9   35662,6    0,0900          
    57,484   1,60186   13317,6  117690,5    0,0900          
    61,283   1,51134    2370,5   23440,4    0,1000          
    66,499   1,40489    2307,9   23039,4    0,1000          
    68,191   1,37410    2518,7   25172,9    0,1000          
    74,275   1,27587     237,7    2276,7    0,1000          
    76,846   1,23946    4965,6   42968,4    0,0900          
    77,209   1,23454    1549,5   15483,1    0,1000          
    80,676   1,18999     258,3    2231,7    0,0900          
    84,329   1,14751     229,7    2294,5    0,1000          
    86,470   1,12451     245,7    2211,5    0,0900          
    88,963   1,09933    1153,7   11452,0    0,1000          
    90,677   1,08296     596,0    6376,5    0,1100          
    91,155   1,07852     382,1    3784,7    0,1000          
    95,217   1,04296     880,7    8781,4    0,1000          
   101,039   0,99798    1374,2   13728,0    0,1000          
   110,951   0,93494     228,9    2514,3    0,1100          
   116,060   0,90800     392,1    4312,2    0,1100          
   116,560   0,90555     968,5   10037,9    0,1100          
   117,816   0,89950     199,4    2127,4    0,1100          
   127,640   0,85834     808,1   11313,6    0,1400          
   129,839   0,85047     474,3    6338,6    0,1400          
   131,032   0,84639     811,5   11144,8    0,1400          
   136,023   0,83071     668,9    9804,3    0,1500          
   142,241   0,81408     430,8    6905,6    0,1700          
   145,119   0,80740     405,0    6802,5    0,1800