1. watch youtube videos - a. betta fighting b. betta breeding
Compare how they swim in each mode. Understand their body language.
2. Totally isolate both male and female for about 3 days. Then let them see each other. Make sure both flare, other wise isolate further and flare the aggressor to a mirror. Keep doing this for about 2 weeks - at the same time mass feed both with highly nutritious foods. . . . . they should flirt swim sometime within that period.
3. While conditioning the pair, set up your tank. Don't use substrates because that will make cleaning difficult (left over food). Anchor your plants with pieces of tiles, small rock, or fishing sinker. Let the whole set up age a bit and give infusoria time to grow (for first day fry food).
4. Aft6er the conditioning period or after they go into breeding mode, put the male in the breeding tank. Float the female in a breeding box or jar. If they still flirting, let them be for a day or two. If still flirting, release the female and let them do their stuff.
Each pair are different. It may take some up to 1 week. So be patient and try not to disturb them too much. As long as they are still in breeding mode, they will eventually spawn.
Good luck