You can register a sow/gilt through the path:
Management> Breeding Herd> Data entry> Females> Purchase > Add
There are three categories of female purchase:
Gilts
Click on the "Add Gilt Purchase" icone
And the following screen will open
Click on this icone 
for an open sow, and this icone 
for a pregnant sow purchase.
After filling all the data just click on the "save and close (if there is no other entry to add) or Save and continue (to add another entry).