Fitting an outside tap can be done in about five minutes.
First turn your water off at the mains, then turn on your garden tap to let any remaining water run out.
Next, remove the old tap. If this is proving difficult, either spray some lubricant in the area where the tap connects to the pipe, or carefully apply heat using a blowtorch, which will cause it to expand and loosen.
Once you’ve removed the old outdoor tap, the tap is out, scrub the inside of the pipe with a hard-bristled toothbrush to clear away any debris.
Now just screw your new brass garden tap onto the pipe by hand, ensuring you avoid any cross threading. Depending on the fitting type, you may need some white plumbers PTFE tape. Once you get to the point where you can’t turn the tap by hand, use an adjustable spanner to tighten the tap up completely.
Then turn on the mains water supply and check if the new outside garden tap is working correctly. If there are any leaks, further tightening may be required.