So why not disconnect the fuse from F7, and put a meter between it and earth; when the relay clicks, the voltage should be 12V, and when the relay is released, the F7 should be 0V (floating). This is actually testing the function you are trying to achieve with the relay!
The fuse F7 plugs in to connect two circuits; one side is the load (and should not change in voltage) and the other side is the supply wire. It is this supply wire (pink and red) that is being moved from terminal #3 to terminal #4.
To paraphrase the instructions for the SmartTop (because saying it another way may help understanding):
My initial recommendation is to find the supply wire on the rear of the fuse 7 slot, and follow that wire (on which you should find a label "7") to where it connects with terminal #3. Undo the nut from that terminal post, and remove only that ring from the post, being sure to put the others back. (Put the nut back on this post now, so none of these can fall off without you noticing) If the ring has more than one wire, cut the other wire(s) off, attach then to a fresh ring, and remount them to terminal #3. (Mine had one small wire). Do up terminal #3.
Undo terminal #4, and attach the wire from fuse 7 and the pink wire from the relay assembly. Do up the nut on terminal #4
Undo terminal #2, and connect the larger terminal with two wires from the relay assembly. do up the nut on terminal #2.
(Sorry to be pedantic about this, but since red/green colour-blindness affects 1/10 males, using red wiring is risky business, so the check for fuse 7 is the test for the right red/pink wire, and does not rely on spotting the colour correctly.)
To test the relay.
Check no wiring other than the complete assembly above has been disturbed. Reconnect teh battery, +ve terminal first, then -ve terminal, being sure to make positive contact at first touch.
If you ground the long black control wire to chassis (bare metal), you should hear the relay click. According to Mods4Cars, you should also hear the small fan start, but there are quite a few noises like that in this area, so you could be misled.
Now remove the fuse #7. Connect one lead of your meter to earth (chassis, bare metal) and use an extended probe into the supply side of Fuse 7. (Note that a paper clip can be bent to form an excellent probe for this purpose
When teh long black wire is grounded, and the relay clicks, you should see 12V at fuse 7, and when the wire is released, the fuse supply should float, showing 0V at the meter. If you do not have 12V, check that you are in fuse 7 (easy trap) and then put the extended probe into the other blade position.
If you still do not have 12V, and you are certain that you have fuse 7, then you will need to check your installation.
(Voltmeter settings should be DC voltage, in the range that covers 12V DC. (probably 20V))