Need help fixing shelves securely on living room wall

Hi, I'm looking for someone experienced to help me fix a couple of shelves in my living room. The walls are a bit tricky as they might be plasterboard, so I want to make sure the shelves are mounted securely and safely to hold books and decorations. I have the shelves and brackets ready, just need the installation done properly. Ideally, someone with their own tools and good knowledge of wall fixings. Looking forward to your help!