Welcome home. Don't feel uncomfortable if you are new or unfamilar with the Episcopal Church. We are all family here so it's unlikely you can do anything one of us has not done ourselves.
Usually we stand or kneel for prayer, sit for instruction, and stand for praise and song. If the service is unfamiliar, just follow the the folk nearby; but remember, you are not required to observe any particular customs and if you want, follow those of your own Church.
All baptized Christians are welcome to receive Holy Communion. The bread is received in the cupped hands or on the tongue. When the chalice bearer comes, you may drink from the chalice or dip the host in the wine. If you choose to drink from the chalice, it is a great help if you will guide it to your lips. Because communion is complete in either form, reception of either bread or wine alone constitutes a full communion.
If you feel uncomfortable taking Communion, simply cross your arms, hands towards shoulders, and the Priest will give you a blessing instead.
There is an annotated explanation of the service here.
Come, share with us, rejoice in the Lord.