There are two ways (on most) engines to find TDC no1 ready to fire. If you happen to have the rocker covers off, bring up the marks and see if no1 valves are closed. If not rotate the crank 1 turn and you will be there
The most popular method is to remove the no1 plug, and "bump" the engine with a finger in the plug hole. When you START to feel compression, look at the marks and carefully wrench or bump the engine up NOT TO TDC but rather the initial timing which you want AKA EG 10BTC or whatever.
Drop in the dist. As others have said, (most) engines so far as firing "don't care " where the rotor points as long as the rotor meets a hole in which no1 wire is inserted. SOME ENGINES do care, some 4's and V6's
If you have a book and know "where" no1 "is supposed to be" drop in the dist accordingly. On some engines like Chev and Ford you may have to diddle the starter to get the thing to fall all the way down into the oil pump drive. Just bring the marks up once more by bumping, again until "the marks" are where you want timing to be.
Rotate the dist body and verify "it sits" where you want and on a Ford the rotor rotates CCW, so you want the rotor "approaching" the no1 tower sort of "corner to corner at the contacts "coming CCW."
If you have points, "rig" a light/ continuity checker, etc to the points, and intentionally retard timing (rotate dist CCW) until points are CLOSED. Now slowly ADVANCE dist (CW on Ford) until points JUST break open on your continuity device. Snug down the dist, install the rest of the wires in order, and START IT UP
Incidentally, the "old traditional Ford" firing order 15426378 is exactly the same as the popular GM/ Mopar one of 18436572 if you re-number the cylinders of one to match the other