It works much better if you do some research first so you will know what will work in your tank, and what you are looking at instead of having to take someone's word that it will work and is healthy.
You need to take into consideration your water, lighting, what substrate you have, what and how many fish, size of tank, maintenance, and lots more. It all makes a difference in which plants will do well for you.
If you give some of this info here people can maybe suggest some plants for you to look into to see if they would be a good fit for your tank.
I am using gravel and I just poked the root end of the plants into the gravel.. Not sure if this is right but they have been in there 3 weeks now and not come loose or died. I have about 5cm deep gravel by the way.
That works well for some plants, but it won't work for all plants. That is why I asked for more info.
Some plants like to be fully planted, some like to be only half planted, some require only the root ends to be planted, some need to be tied to something (not planted at all), and some need to float on top. There are many that you can do any way you prefer. It just depends on the plant and the set up.
Tropica is a good site for info too. The pinned topics here are also very helpful. If you still have questions, give us some info to go on and ask away.