If you need to find articles on a TOPIC or SUBJECT, use one of our databases. Databases collect article references from many sources so you can search broadly.
If you have a reference and you want to FIND AN EXACT ARTICLE, use the A-to-Z journal list. Search for the journal title and follow the links to the full text.
Alternately, you can use Google Scholar, which is pretty good at locating EXACT article titles.
Probably not unless you plan on publishing your work publically (thesis or dissertation, journal article, etc). If you want to reuse images/figures from another author in your published work use the Copyright Clearance Center to find permission rules for various publishers.
You can also email the librarian for more help.
A properly sourced PowerPoint (or other slide software) presentation has two features - a list of references at the end and specific citations as needed.
Use the ACS Style Guide, 3rd. Ed., Chapter 14 for formatting guidelines and create a slide at the end with your references. If your sources do not all comfortably fit on one slide, put up the most important ones on the slide and "complete references available upon request" or something similar towards the bottom of the slide. If you are directly quoting, a page number or page range should be included.
In a presentation you can cite your sources two main ways.
1. Verbal citation - you can mention the work and author before discussing their contribution, example "As Dr. Bigshot said in her 2009 Science paper..." Works you verbally cite still need to appear in the reference list.
2. Written - After you use something taken from a source, cite it. Author parenthetical is probably the easiest and least intrusive citation method. Example - (Bigshot, 2009).
Cite using common sense (Chapter 14, p. 290)-
'The market for this product was $31 million in 2011 (Bigshot, 2009)'
'As Bigshot (2009) said...'
'This product has two notable advantages - it doesn't cause cancer and does not explode (Bigshot, 2009).'
If you are using a figure from a piece of scholarly literature that is in your reference list, cite as normal. If you were to publish your PowerPoint broadly, you would need copyright clearance but this is not relevant for a student presentation.
If it is a image from a website, think about searching on WikiMedia Commons and follow the attribution rules. There are millions of images freely usable on the web with a simple attribution. Generally I use a smaller font and a lighter font color at the bottom of the slide to source my PowerPoint images using "Photo <copyright holder>, <url>". Do not put images used as decoration in your reference list.
You can also use Google Images, under "Search Tools" select "Usage Rights" and "Labelled for Noncommercial Reuse" to ethically find images. (Screenshot below)
ACS Style is the most common citation style for chemists.