In silicoPCR searches a seuence database with a pair of PCR primers, using an indexing strategy for fast perfomance. In silico PCR is available only for nucleic sequences. To use it in UGENE open a DNA sequence and go to the In Silico PCR tab of the Options Panel:

Here the following parameters are available:
Forward primer - forward primer.
Reverse primer - on the opposite strand from the forward primer.
Mismatches - mismatches.
Maximum product - maximum size of amplified region.