How to remove malicious file

I received notice that my website was sending out malicious email with a spoofed user. I’ve fixed the issue with an update but now I need to remove the malicious file.

WPscan gives me the following:

[!] Title: LayerSlider 4.6.1 – Style Editing CSRF
Reference: https://wpvulndb.com/vulnerabilities/7152
Reference: https://packetstormsecurity.com/files/125637/
[i] Fixed in: 5.2.0

[!] Title: LayerSlider 4.6.1 – Remote Path Traversal File Access
Reference: https://wpvulndb.com/vulnerabilities/7153
Reference: https://packetstormsecurity.com/files/125637/
Reference: https://secunia.com/advisories/57309/
[i] Fixed in: 5.2.0

[!] Title: WordPress Slider Revolution Local File Disclosure
Reference: https://wpvulndb.com/vulnerabilities/7540
Reference: https://blog.sucuri.net/2014/09/slider-revolution-plugin-critical-vulnerability-being-exploited.html
Reference: https://packetstormsecurity.com/files/129761/
Reference: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-1579
Reference: https://www.exploit-db.com/exploits/34511/
Reference: https://www.exploit-db.com/exploits/36039/
[i] Fixed in: 4.1.5

[!] Title: WordPress Slider Revolution Shell Upload
Reference: https://wpvulndb.com/vulnerabilities/7954
Reference: https://whatisgon.wordpress.com/2014/11/30/another-revslider-vulnerability/
Reference: https://www.rapid7.com/db/modules/exploit/unix/webapp/wp_revslider_upload_execute
Reference: https://www.exploit-db.com/exploits/35385/
[i] Fixed in: 3.0.96

Any idea how to remove the malicious file?