Is this not available without paying?
No. You can do this for free. Start the Rectangle tool, click to set the first corner and then drag out to make a rectangle. Type the dimensions you want and hit Enter. This is a very basic operation. You should look at the tutorial videos available at sketchup.com and learn how the program works.
As DaveR says, “just type in the size”…
BUT, also note this… you must type in the size immediately after picking the second corner, and you must separate the length and width with a comma and press the [enter] button to confirm the size.
If you live in a locale where you type a comma as a decimal point then you need to use a semicolon instead.
So in the USA, UK, Aus etc it’s:
but in Latin countries and much of the EU it’s:
Only ever include a space in your typed in dimensions if you are inputting fractional inches, e.g.
Don’t put them after the separating comma/semicolon…
You don’t need to include a units suffix [unless it’s in '/"], because SketchUp assumes a typed in number is in the current Model Info > Units, but if you do add a suffix it is converted anyway - so if you are working in meters and type 10 it assumes 10m, but you can type in 100mm and SketchUp draws that line 0.1m long - making live much easier
Tip: draw an approximation of the desired rectangle, so the bigger dimension is obvious on screen, and you can also see which dimension is which in the current text displayed in the Measurements box, so you'll know which order to type the sizes in - sometimes which is the length and which is the width might not be obvious, especially in 3d space...
thanks to you both i think i have a lot of learning to do