Step 1: download PS3 tools in here https://www.psx-place.com/resources/ps3-tools-collection.594/
Step 2: Hover your mouse pointer over the eboot or sprx file and right click
and then click on properties and change Open with as pkg file and then click on apply then click on Ok
Step 3:Right click the file again and press SELF tools and then click on resign EBOOT/SELF
OPTIONAL
You can automatically resign other sprx files or eboot if the files are in the same folder
Step 2: Hover your mouse pointer over the eboot or sprx file and right click
and then click on properties and change Open with as pkg file and then click on apply then click on Ok
Step 3:Right click the file again and press SELF tools and then click on resign EBOOT/SELF
OPTIONAL
You can automatically resign other sprx files or eboot if the files are in the same folder