"To share an agenda" means to have a common goal or objective with others and work towards it together. It implies cooperating, collaborating, and being on the same page regarding a specific plan or purpose. Full definition
They are the elected representatives who ostensibly share an agenda with the governor and, in theory, work with him to pass laws. (gothamgazette.com)
The artists share no agenda or style; they are simply trying to make paintings that reflect how they interact with and process their world. (painters-table.com)
There is a written shared agenda — and it's followed in the meeting. (theeffectiveadmin.com)