Three serious typographical flaws of Scribus still unsolved are:
1. automatic activation/deactivation of ligatures,
2. mechanism to automatically switch between upper/lowercase letters and Small Caps (I mean "real" small caps provided by fonts, not these terrible "poor man" faked ones you get by pressing "Small Caps" button in "Properties" palette), and
3. automatic replacement of lining figures with text figures (i.e., old style numbers).
So, you have two options:
1. To manually enter text figures using Insert > Glyphs dialog, or
2. After you've finished editing your document, use Search-Replace for every number. Note that this works per linked text frame, meaning if you have unlinked text frames, you'll have to do Search-Replace for every single one of them.
There are another two possibilities:
1. Use fonts which have text figures activated as default numbers, while lining figures must be activated explicitly (e.g., most fonts made by Type-Together and exljbris foundries).
2. If the licence allows, you might edit font files and replace lining figures with text figures. However, this might not be an optimal solution since kerning might get messed up.