From the factory your X1/9 would have had sealed beam headlights; 6024 or H6024, the latter being the halogen variety. A somewhat poplar upgrade is to use European style headlights with H4 bulbs, so check what you have.
If the car is wired for sealed beams, and the harness is made for H4, you will need to make changes to the relay harness. The harness will have two 3-position sockets that fit on the bulbs. If you are staying with sealed beam headlights, or using LED sealed beam replacements, you will need to modify the wiring to both sockets. Found on Amazon.com:
View attachment 56430
If you are converting to H4, then the two sockets can stay as they are.
The relay harness also has a 3-position plug that looks like the pins on the back of the bulb. If the car wiring is stock, you'll need to change the wiring to this plug regardless of what bulbs you will be using. The change is, in principle, the same as above, but keep in mind it will be mirror image, since you are looking at the plug, not the socket it mates with.