Amplifiers are designed to work with speakers and will have speaker terminals already installed. Connecting speakers to an amplifier is as simple as plugging them into the appropriate terminals.
Speaker wire is not differential, meaning that both ends of the wire are the same and can be connected in either direction. The most common speaker connections are either a screw terminal or a push-fit terminal, but the specific terminals on your amplifier and speakers will vary depending on their design.
Generally in the UK, one speaker connection will be coloured black, while the other will be red. They tend to be marked the same on the amplifier and the speaker. If no colours are present then a + and a – will indicate the connection, usually.