Whichever method you choose make sure you cut your light strip along the designated cut points to ensure your lights will work if necessary.
Connect 2 led strips together.
The main challenge is that most power supply units will only have one of each positive and negative output wires so to connect that to more than one led strip section will require you to split that output into multiple wires.
Two or more one color led strips to the power supply more led strips can be attached if the power supply and the transformer is powerful enough to support it depending on output wattage.
Heat up the soldering iron until it smokes a little bit.
Purchase led lights and all the connections.
Often referred to as daisy chained or looped the current in a series circuit follows one path from start to finish with the anode positive of the second led connected to the cathode negative of the first.
Put only a little bit of solder on the tip of the rgb wires and melt it thoroughly.
To connect the multiple strips a connector block is used which is known to split the power supply into many outputs.
Place your led strips on the table and use a tape to hold them down so that they don t move.
It looks like your strip is analog control and not digital which would have little ics in the strip to control individual led color so the specific color ground lines are all in parallel.
Clean the tips of the two led strips that you want to connect thoroughly.
You should be able to connect numerous strips in parallel 12v to 12v red to red green to green and blue to blue to blue.