Most of the gods will have chants associated with them for invoking them, but if you do not have one yet specific for you, you can just use one of the Esperanto basic calling chants. The three of them are:

Sacred is ___, They are here. - sankta estas ___, ili estas ĉi tie (Any gender)

Sacred is ___, He is here. - sankta estas ___, lie estas ĉi tie (Masculine)

Sacred is ___, She is here. - sankta estas ___, ŝi estas ĉi tie. (Feminine)

Try using these for the god you have a certain amount of affinity for already. I translated them into Esperanto but really you can use any language. Chant them for a few minutes at a time if you have no experience with this stuff, then gradually increase until you talk to the gods.