So the piece is likely the first volume/chapter of a story where the protagonist's older sister is a yanmama (a mother with a yankee — delinquent/ganguro style — personality) and is currently breastfeeding. The content is almost certainly adult-oriented (erotic or comedic with adult themes).
To successfully install "ane wa yanmama junyuuchuu 1", follow these steps: ane wa yanmama junyuuchuu 1 install
= probably refers to installing a digital version (e.g., from DLsite or a game patch) or could be part of a filename for a downloaded archive So the piece is likely the first volume/chapter