
Summoning techniques are... well bad a**.
In order to learn one you need to learn the "Summoning Technique" (C-Rank) and then make a pact with the creature you want to summon. (Contact Staff)
If you use it without a contract- it's VERY dangerous and can kill you. However the alternative is that you end up being reverse summoned to the location of the creature that most represents you.
To make a contract, you need to do training (once you've located the beast). They are generally C or B rank.